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1 | <?xml version="1.0" encoding="ISO-8859-1"?> |
2 | <!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.3//EN" | |
3 | "http://www.oasis-open.org/docbook/xml/4.3/docbookx.dtd" [ | |
4 | <!ENTITY % defs SYSTEM "/xserver/doc/xml/xserver.ent"> %defs; | |
5 | ]> | |
6 | ||
7 | <article> | |
8 | ||
9 | <articleinfo> | |
10 | <!-- Title information --> | |
11 | <title>Distributed Multihead X design</title> | |
12 | <authorgroup> | |
13 | <author><firstname>Kevin E.</firstname><surname>Martin</surname></author> | |
14 | <author><firstname>David H.</firstname><surname>Dawes</surname></author> | |
15 | <author><firstname>Rickard E.</firstname><surname>Faith</surname></author> | |
16 | </authorgroup> | |
17 | <pubdate>29 June 2004 (created 25 July 2001)</pubdate> | |
18 | <releaseinfo>X Server Version &xserver.version;</releaseinfo> | |
19 | <abstract><para> | |
20 | This document covers the motivation, background, design, and | |
21 | implementation of the distributed multihead X (DMX) system. It | |
22 | is a living document and describes the current design and | |
23 | implementation details of the DMX system. As the project | |
24 | progresses, this document will be continually updated to reflect | |
25 | the changes in the code and/or design. <emphasis remap="it">Copyright 2001 by VA | |
26 | Linux Systems, Inc., Fremont, California. Copyright 2001-2004 | |
27 | by Red Hat, Inc., Raleigh, North Carolina</emphasis> | |
28 | </para></abstract> | |
29 | </articleinfo> | |
30 | ||
31 | <!-- Begin the document --> | |
32 | <sect1> | |
33 | <title>Introduction</title> | |
34 | ||
35 | <sect2> | |
36 | <title>The Distributed Multihead X Server</title> | |
37 | ||
38 | <para>Current Open Source multihead solutions are limited to a single | |
39 | physical machine. A single X server controls multiple display devices, | |
40 | which can be arranged as independent heads or unified into a single | |
41 | desktop (with Xinerama). These solutions are limited to the number of | |
42 | physical devices that can co-exist in a single machine (e.g., due to the | |
43 | number of AGP/PCI slots available for graphics cards). Thus, large | |
44 | tiled displays are not currently possible. The work described in this | |
45 | paper will eliminate the requirement that the display devices reside in | |
46 | the same physical machine. This will be accomplished by developing a | |
47 | front-end proxy X server that will control multiple back-end X servers | |
48 | that make up the large display. | |
49 | </para> | |
50 | ||
51 | <para>The overall structure of the distributed multihead X (DMX) project is | |
52 | as follows: A single front-end X server will act as a proxy to a set of | |
53 | back-end X servers, which handle all of the visible rendering. X | |
54 | clients will connect to the front-end server just as they normally would | |
55 | to a regular X server. The front-end server will present an abstracted | |
56 | view to the client of a single large display. This will ensure that all | |
57 | standard X clients will continue to operate without modification | |
58 | (limited, as always, by the visuals and extensions provided by the X | |
59 | server). Clients that are DMX-aware will be able to use an extension to | |
60 | obtain information about the back-end servers (e.g., for placement of | |
61 | pop-up windows, window alignments by the window manager, etc.). | |
62 | </para> | |
63 | ||
64 | <para>The architecture of the DMX server is divided into two main sections: | |
65 | input (e.g., mouse and keyboard events) and output (e.g., rendering and | |
66 | windowing requests). Each of these are describe briefly below, and the | |
67 | rest of this design document will describe them in greater detail. | |
68 | </para> | |
69 | ||
70 | <para>The DMX server can receive input from three general types of input | |
71 | devices: "local" devices that are physically attached to the machine on | |
72 | which DMX is running, "backend" devices that are physically attached to | |
73 | one or more of the back-end X servers (and that generate events via the | |
74 | X protocol stream from the backend), and "console" devices that can be | |
75 | abstracted from any non-back-end X server. Backend and console devices | |
76 | are treated differently because the pointer device on the back-end X | |
77 | server also controls the location of the hardware X cursor. Full | |
78 | support for XInput extension devices is provided. | |
79 | </para> | |
80 | ||
81 | <para>Rendering requests will be accepted by the front-end server; however, | |
82 | rendering to visible windows will be broken down as needed and sent to | |
83 | the appropriate back-end server(s) via X11 library calls for actual | |
84 | rendering. The basic framework will follow a Xnest-style approach. GC | |
85 | state will be managed in the front-end server and sent to the | |
86 | appropriate back-end server(s) as required. Pixmap rendering will (at | |
87 | least initially) be handled by the front-end X server. Windowing | |
88 | requests (e.g., ordering, mapping, moving, etc.) will handled in the | |
89 | front-end server. If the request requires a visible change, the | |
90 | windowing operation will be translated into requests for the appropriate | |
91 | back-end server(s). Window state will be mirrored in the back-end | |
92 | server(s) as needed. | |
93 | </para> | |
94 | </sect2> | |
95 | ||
96 | <sect2> | |
97 | <title>Layout of Paper</title> | |
98 | ||
99 | <para>The next section describes the general development plan that was | |
100 | actually used for implementation. The final section discusses | |
101 | outstanding issues at the conclusion of development. The first appendix | |
102 | provides low-level technical detail that may be of interest to those | |
103 | intimately familiar with the X server architecture. The final appendix | |
104 | describes the four phases of development that were performed during the | |
105 | first two years of development. | |
106 | </para> | |
107 | ||
108 | <para>The final year of work was divided into 9 tasks that are not | |
109 | described in specific sections of this document. The major tasks during | |
110 | that time were the enhancement of the reconfiguration ability added in | |
111 | Phase IV, addition of support for a dynamic number of back-end displays | |
112 | (instead of a hard-coded limit), and the support for back-end display | |
113 | and input removal and addition. This work is mentioned in this paper, | |
114 | but is not covered in detail. | |
115 | </para> | |
116 | </sect2> | |
117 | </sect1> | |
118 | ||
119 | <!-- ============================================================ --> | |
120 | <sect1> | |
121 | <title>Development plan</title> | |
122 | ||
123 | <para>This section describes the development plan from approximately June | |
124 | 2001 through July 2003. | |
125 | </para> | |
126 | ||
127 | <sect2> | |
128 | <title>Bootstrap code</title> | |
129 | ||
130 | <para>To allow for rapid development of the DMX server by multiple | |
131 | developers during the first development stage, the problem will be | |
132 | broken down into three tasks: the overall DMX framework, back-end | |
133 | rendering services and input device handling services. However, before | |
134 | the work begins on these tasks, a simple framework that each developer | |
135 | could use was implemented to bootstrap the development effort. This | |
136 | framework renders to a single back-end server and provides dummy input | |
137 | devices (i.e., the keyboard and mouse). The simple back-end rendering | |
138 | service was implemented using the shadow framebuffer support currently | |
139 | available in the XFree86 environment. | |
140 | </para> | |
141 | ||
142 | <para>Using this bootstrapping framework, each developer has been able to | |
143 | work on each of the tasks listed above independently as follows: the | |
144 | framework will be extended to handle arbitrary back-end server | |
145 | configurations; the back-end rendering services will be transitioned to | |
146 | the more efficient Xnest-style implementation; and, an input device | |
147 | framework to handle various input devices via the input extension will | |
148 | be developed. | |
149 | </para> | |
150 | ||
151 | <para>Status: The boot strap code is complete. <!-- August 2001 --> | |
152 | </para> | |
153 | ||
154 | </sect2> | |
155 | ||
156 | <sect2> | |
157 | <title>Input device handling</title> | |
158 | ||
159 | <para>An X server (including the front-end X server) requires two core | |
160 | input devices -- a keyboard and a pointer (mouse). These core devices | |
161 | are handled and required by the core X11 protocol. Additional types of | |
162 | input devices may be attached and utilized via the XInput extension. | |
163 | These are usually referred to as ``XInput extension devices'', | |
164 | </para> | |
165 | ||
166 | <para>There are some options as to how the front-end X server gets its core | |
167 | input devices: | |
168 | ||
169 | <orderedlist> | |
170 | <listitem> | |
171 | <para>Local Input. The physical input devices (e.g., keyboard and | |
172 | mouse) can be attached directly to the front-end X server. In this | |
173 | case, the keyboard and mouse on the machine running the front-end X | |
174 | server will be used. The front-end will have drivers to read the | |
175 | raw input from those devices and convert it into the required X | |
176 | input events (e.g., key press/release, pointer button press/release, | |
177 | pointer motion). The front-end keyboard driver will keep track of | |
178 | keyboard properties such as key and modifier mappings, autorepeat | |
179 | state, keyboard sound and led state. Similarly the front-end | |
180 | pointer driver will keep track if pointer properties such as the | |
181 | button mapping and movement acceleration parameters. With this | |
182 | option, input is handled fully in the front-end X server, and the | |
183 | back-end X servers are used in a display-only mode. This option was | |
184 | implemented and works for a limited number of Linux-specific | |
185 | devices. Adding additional local input devices for other | |
186 | architectures is expected to be relatively simple. | |
187 | </para> | |
188 | ||
189 | <para>The following options are available for implementing local input | |
190 | devices: | |
191 | ||
192 | <orderedlist> | |
193 | <listitem> | |
194 | <para>The XFree86 X server has modular input drivers that could | |
195 | be adapted for this purpose. The mouse driver supports a wide | |
196 | range of mouse types and interfaces, as well as a range of | |
197 | Operating System platforms. The keyboard driver in XFree86 is | |
198 | not currently as modular as the mouse driver, but could be made | |
199 | so. The XFree86 X server also has a range of other input | |
200 | drivers for extended input devices such as tablets and touch | |
201 | screens. Unfortunately, the XFree86 drivers are generally | |
202 | complex, often simultaneously providing support for multiple | |
203 | devices across multiple architectures; and rely so heavily on | |
204 | XFree86-specific helper-functions, that this option was not | |
205 | pursued. | |
206 | </para> | |
207 | </listitem> | |
208 | ||
209 | <listitem> | |
210 | <para>The <command>kdrive</command> X server in XFree86 has built-in drivers that | |
211 | support PS/2 mice and keyboard under Linux. The mouse driver | |
212 | can indirectly handle other mouse types if the Linux utility | |
213 | <command>gpm</command> is used as to translate the native mouse protocol into | |
214 | PS/2 mouse format. These drivers could be adapted and built in | |
215 | to the front-end X server if this range of hardware and OS | |
216 | support is sufficient. While much simpler than the XFree86 | |
217 | drivers, the <command>kdrive</command> drivers were not used for the DMX | |
218 | implementation. | |
219 | </para> | |
220 | </listitem> | |
221 | ||
222 | <listitem> | |
223 | <para>Reimplementation of keyboard and mouse drivers from | |
224 | scratch for the DMX framework. Because keyboard and mouse | |
225 | drivers are relatively trivial to implement, this pathway was | |
226 | selected. Other drivers in the X source tree were referenced, | |
227 | and significant contributions from other drivers are noted in | |
228 | the DMX source code. | |
229 | </para> | |
230 | </listitem> | |
231 | </orderedlist> | |
232 | </para> | |
233 | </listitem> | |
234 | ||
235 | <listitem> | |
236 | <para>Backend Input. The front-end can make use of the core input | |
237 | devices attached to one or more of the back-end X servers. Core | |
238 | input events from multiple back-ends are merged into a single input | |
239 | event stream. This can work sanely when only a single set of input | |
240 | devices is used at any given time. The keyboard and pointer state | |
241 | will be handled in the front-end, with changes propagated to the | |
242 | back-end servers as needed. This option was implemented and works | |
243 | well. Because the core pointer on a back-end controls the hardware | |
244 | mouse on that back-end, core pointers cannot be treated as XInput | |
245 | extension devices. However, all back-end XInput extensions devices | |
246 | can be mapped to either DMX core or DMX XInput extension devices. | |
247 | </para> | |
248 | </listitem> | |
249 | ||
250 | <listitem> | |
251 | <para>Console Input. The front-end server could create a console | |
252 | window that is displayed on an X server independent of the back-end | |
253 | X servers. This console window could display things like the | |
254 | physical screen layout, and the front-end could get its core input | |
255 | events from events delivered to the console window. This option was | |
256 | implemented and works well. To help the human navigate, window | |
257 | outlines are also displayed in the console window. Further, console | |
258 | windows can be used as either core or XInput extension devices. | |
259 | </para> | |
260 | </listitem> | |
261 | ||
262 | <listitem> | |
263 | <para>Other options were initially explored, but they were all | |
264 | partial subsets of the options listed above and, hence, are | |
265 | irrelevant. | |
266 | </para> | |
267 | </listitem> | |
268 | ||
269 | </orderedlist> | |
270 | </para> | |
271 | ||
272 | <para>Although extended input devices are not specifically mentioned in the | |
273 | Distributed X requirements, the options above were all implemented so | |
274 | that XInput extension devices were supported. | |
275 | </para> | |
276 | ||
277 | <para>The bootstrap code (Xdmx) had dummy input devices, and these are | |
278 | still supported in the final version. These do the necessary | |
279 | initialization to satisfy the X server's requirements for core pointer | |
280 | and keyboard devices, but no input events are ever generated. | |
281 | </para> | |
282 | ||
283 | <para>Status: The input code is complete. Because of the complexity of the | |
284 | XFree86 input device drivers (and their heavy reliance on XFree86 | |
285 | infrastructure), separate low-level device drivers were implemented for | |
286 | Xdmx. The following kinds of drivers are supported (in general, the | |
287 | devices can be treated arbitrarily as "core" input devices or as XInput | |
288 | "extension" devices; and multiple instances of different kinds of | |
289 | devices can be simultaneously available): | |
290 | <orderedlist> | |
291 | <listitem> | |
292 | <para> A "dummy" device drive that never generates events. | |
293 | </para> | |
294 | </listitem> | |
295 | ||
296 | <listitem> | |
297 | <para> "Local" input is from the low-level hardware on which the | |
298 | Xdmx binary is running. This is the only area where using the | |
299 | XFree86 driver infrastructure would have been helpful, and then | |
300 | only partially, since good support for generic USB devices does | |
301 | not yet exist in XFree86 (in any case, XFree86 and kdrive driver | |
302 | code was used where possible). Currently, the following local | |
303 | devices are supported under Linux (porting to other operating | |
304 | systems should be fairly straightforward): | |
305 | <itemizedlist> | |
306 | <listitem><para>Linux keyboard</para></listitem> | |
307 | <listitem><para>Linux serial mouse (MS)</para></listitem> | |
308 | <listitem><para>Linux PS/2 mouse</para></listitem> | |
309 | <listitem><para>USB keyboard</para></listitem> | |
310 | <listitem><para>USB mouse</para></listitem> | |
311 | <listitem><para>USB generic device (e.g., joystick, gamepad, etc.)</para></listitem> | |
312 | </itemizedlist> | |
313 | </para> | |
314 | </listitem> | |
315 | ||
316 | <listitem> | |
317 | <para> "Backend" input is taken from one or more of the back-end | |
318 | displays. In this case, events are taken from the back-end X | |
319 | server and are converted to Xdmx events. Care must be taken so | |
320 | that the sprite moves properly on the display from which input | |
321 | is being taken. | |
322 | </para> | |
323 | </listitem> | |
324 | ||
325 | <listitem> | |
326 | <para> "Console" input is taken from an X window that Xdmx | |
327 | creates on the operator's display (i.e., on the machine running | |
328 | the Xdmx binary). When the operator's mouse is inside the | |
329 | console window, then those events are converted to Xdmx events. | |
330 | Several special features are available: the console can display | |
331 | outlines of windows that are on the Xdmx display (to facilitate | |
332 | navigation), the cursor can be confined to the console, and a | |
333 | "fine" mode can be activated to allow very precise cursor | |
334 | positioning. | |
335 | </para> | |
336 | </listitem> | |
337 | </orderedlist> | |
338 | ||
339 | </para> | |
340 | ||
341 | </sect2> | |
342 | ||
343 | <!-- May 2002; July 2003 --> | |
344 | ||
345 | <sect2> | |
346 | <title>Output device handling</title> | |
347 | ||
348 | <para>The output of the DMX system displays rendering and windowing | |
349 | requests across multiple screens. The screens are typically arranged in | |
350 | a grid such that together they represent a single large display. | |
351 | </para> | |
352 | ||
353 | <para>The output section of the DMX code consists of two parts. The first | |
354 | is in the front-end proxy X server (Xdmx), which accepts client | |
355 | connections, manages the windows, and potentially renders primitives but | |
356 | does not actually display any of the drawing primitives. The second | |
357 | part is the back-end X server(s), which accept commands from the | |
358 | front-end server and display the results on their screens. | |
359 | </para> | |
360 | ||
361 | <sect3> | |
362 | <title>Initialization</title> | |
363 | ||
364 | <para>The DMX front-end must first initialize its screens by connecting to | |
365 | each of the back-end X servers and collecting information about each of | |
366 | these screens. However, the information collected from the back-end X | |
367 | servers might be inconsistent. Handling these cases can be difficult | |
368 | and/or inefficient. For example, a two screen system has one back-end X | |
369 | server running at 16bpp while the second is running at 32bpp. | |
370 | Converting rendering requests (e.g., XPutImage() or XGetImage() | |
371 | requests) to the appropriate bit depth can be very time consuming. | |
372 | Analyzing these cases to determine how or even if it is possible to | |
373 | handle them is required. The current Xinerama code handles many of | |
374 | these cases (e.g., in PanoramiXConsolidate()) and will be used as a | |
375 | starting point. In general, the best solution is to use homogeneous X | |
376 | servers and display devices. Using back-end servers with the same depth | |
377 | is a requirement of the final DMX implementation. | |
378 | </para> | |
379 | ||
380 | <para>Once this screen consolidation is finished, the relative position of | |
381 | each back-end X server's screen in the unified screen is initialized. A | |
382 | full-screen window is opened on each of the back-end X servers, and the | |
383 | cursor on each screen is turned off. The final DMX implementation can | |
384 | also make use of a partial-screen window, or multiple windows per | |
385 | back-end screen. | |
386 | </para> | |
387 | </sect3> | |
388 | ||
389 | <sect3> | |
390 | <title>Handling rendering requests</title> | |
391 | ||
392 | <para>After initialization, X applications connect to the front-end server. | |
393 | There are two possible implementations of how rendering and windowing | |
394 | requests are handled in the DMX system: | |
395 | ||
396 | <orderedlist> | |
397 | <listitem> | |
398 | <para>A shadow framebuffer is used in the front-end server as the | |
399 | render target. In this option, all protocol requests are completely | |
400 | handled in the front-end server. All state and resources are | |
401 | maintained in the front-end including a shadow copy of the entire | |
402 | framebuffer. The framebuffers attached to the back-end servers are | |
403 | updated by XPutImage() calls with data taken directly from the | |
404 | shadow framebuffer. | |
405 | </para> | |
406 | ||
407 | <para>This solution suffers from two main problems. First, it does not | |
408 | take advantage of any accelerated hardware available in the system. | |
409 | Second, the size of the XPutImage() calls can be quite large and | |
410 | thus will be limited by the bandwidth available. | |
411 | </para> | |
412 | ||
413 | <para>The initial DMX implementation used a shadow framebuffer by | |
414 | default. | |
415 | </para> | |
416 | </listitem> | |
417 | ||
418 | <listitem> | |
419 | <para>Rendering requests are sent to each back-end server for | |
420 | handling (as is done in the Xnest server described above). In this | |
421 | option, certain protocol requests are handled in the front-end | |
422 | server and certain requests are repackaged and then sent to the | |
423 | back-end servers. The framebuffer is distributed across the | |
424 | multiple back-end servers. Rendering to the framebuffer is handled | |
425 | on each back-end and can take advantage of any acceleration | |
426 | available on the back-end servers' graphics display device. State | |
427 | is maintained both in the front and back-end servers. | |
428 | </para> | |
429 | ||
430 | <para>This solution suffers from two main drawbacks. First, protocol | |
431 | requests are sent to all back-end servers -- even those that will | |
432 | completely clip the rendering primitive -- which wastes bandwidth | |
433 | and processing time. Second, state is maintained both in the front- | |
434 | and back-end servers. These drawbacks are not as severe as in | |
435 | option 1 (above) and can either be overcome through optimizations or | |
436 | are acceptable. Therefore, this option will be used in the final | |
437 | implementation. | |
438 | </para> | |
439 | ||
440 | <para>The final DMX implementation defaults to this mechanism, but also | |
441 | supports the shadow framebuffer mechanism. Several optimizations | |
442 | were implemented to eliminate the drawbacks of the default | |
443 | mechanism. These optimizations are described the section below and | |
444 | in Phase II of the Development Results (see appendix). | |
445 | </para> | |
446 | </listitem> | |
447 | ||
448 | </orderedlist> | |
449 | </para> | |
450 | ||
451 | <para>Status: Both the shadow framebuffer and Xnest-style code is complete. | |
452 | <!-- May 2002 --> | |
453 | </para> | |
454 | ||
455 | </sect3> | |
456 | </sect2> | |
457 | ||
458 | <sect2> | |
459 | <title>Optimizing DMX</title> | |
460 | ||
461 | <para>Initially, the Xnest-style solution's performance will be measured | |
462 | and analyzed to determine where the performance bottlenecks exist. | |
463 | There are four main areas that will be addressed. | |
464 | </para> | |
465 | ||
466 | <para>First, to obtain reasonable interactivity with the first development | |
467 | phase, XSync() was called after each protocol request. The XSync() | |
468 | function flushes any pending protocol requests. It then waits for the | |
469 | back-end to process the request and send a reply that the request has | |
470 | completed. This happens with each back-end server and performance | |
471 | greatly suffers. As a result of the way XSync() is called in the first | |
472 | development phase, the batching that the X11 library performs is | |
473 | effectively defeated. The XSync() call usage will be analyzed and | |
474 | optimized by batching calls and performing them at regular intervals, | |
475 | except where interactivity will suffer (e.g., on cursor movements). | |
476 | </para> | |
477 | ||
478 | <para>Second, the initial Xnest-style solution described above sends the | |
479 | repackaged protocol requests to all back-end servers regardless of | |
480 | whether or not they would be completely clipped out. The requests that | |
481 | are trivially rejected on the back-end server wastes the limited | |
482 | bandwidth available. By tracking clipping changes in the DMX X server's | |
483 | windowing code (e.g., by opening, closing, moving or resizing windows), | |
484 | we can determine whether or not back-end windows are visible so that | |
485 | trivial tests in the front-end server's GC ops drawing functions can | |
486 | eliminate these unnecessary protocol requests. | |
487 | </para> | |
488 | ||
489 | <para>Third, each protocol request will be analyzed to determine if it is | |
490 | possible to break the request into smaller pieces at display boundaries. | |
491 | The initial ones to be analyzed are put and get image requests since | |
492 | they will require the greatest bandwidth to transmit data between the | |
493 | front and back-end servers. Other protocol requests will be analyzed | |
494 | and those that will benefit from breaking them into smaller requests | |
495 | will be implemented. | |
496 | </para> | |
497 | ||
498 | <para>Fourth, an extension is being considered that will allow font glyphs to | |
499 | be transferred from the front-end DMX X server to each back-end server. | |
500 | This extension will permit the front-end to handle all font requests and | |
501 | eliminate the requirement that all back-end X servers share the exact | |
502 | same fonts as the front-end server. We are investigating the | |
503 | feasibility of this extension during this development phase. | |
504 | </para> | |
505 | ||
506 | <para>Other potential optimizations will be determined from the performance | |
507 | analysis. | |
508 | </para> | |
509 | ||
510 | <para>Please note that in our initial design, we proposed optimizing BLT | |
511 | operations (e.g., XCopyArea() and window moves) by developing an | |
512 | extension that would allow individual back-end servers to directly copy | |
513 | pixel data to other back-end servers. This potential optimization was | |
514 | in response to the simple image movement implementation that required | |
515 | potentially many calls to GetImage() and PutImage(). However, the | |
516 | current Xinerama implementation handles these BLT operations | |
517 | differently. Instead of copying data to and from screens, they generate | |
518 | expose events -- just as happens in the case when a window is moved from | |
519 | off a screen to on screen. This approach saves the limited bandwidth | |
520 | available between front and back-end servers and is being standardized | |
521 | with Xinerama. It also eliminates the potential setup problems and | |
522 | security issues resulting from having each back-end server open | |
523 | connections to all other back-end servers. Therefore, we suggest | |
524 | accepting Xinerama's expose event solution. | |
525 | </para> | |
526 | ||
527 | <para>Also note that the approach proposed in the second and third | |
528 | optimizations might cause backing store algorithms in the back-end to be | |
529 | defeated, so a DMX X server configuration flag will be added to disable | |
530 | these optimizations. | |
531 | </para> | |
532 | ||
533 | <para>Status: The optimizations proposed above are complete. It was | |
534 | determined that the using the xfs font server was sufficient and | |
535 | creating a new mechanism to pass glyphs was redundant; therefore, the | |
536 | fourth optimization proposed above was not included in DMX. | |
537 | <!-- September 2002 --> | |
538 | </para> | |
539 | ||
540 | </sect2> | |
541 | ||
542 | <sect2> | |
543 | <title>DMX X extension support</title> | |
544 | ||
545 | <para>The DMX X server keeps track of all the windowing information on the | |
546 | back-end X servers, but does not currently export this information to | |
547 | any client applications. An extension will be developed to pass the | |
548 | screen information and back-end window IDs to DMX-aware clients. These | |
549 | clients can then use this information to directly connect to and render | |
550 | to the back-end windows. Bypassing the DMX X server allows DMX-aware | |
551 | clients to break up complex rendering requests on their own and send | |
552 | them directly to the windows on the back-end server's screens. An | |
553 | example of a client that can make effective use of this extension is | |
554 | Chromium. | |
555 | </para> | |
556 | ||
557 | <para>Status: The extension, as implemented, is fully documented in | |
558 | "Client-to-Server DMX Extension to the X Protocol". Future changes | |
559 | might be required based on feedback and other proposed enhancements to | |
560 | DMX. Currently, the following facilities are supported: | |
561 | <orderedlist> | |
562 | <listitem><para> | |
563 | Screen information (clipping rectangle for each screen relative | |
564 | to the virtual screen) | |
565 | </para></listitem> | |
566 | <listitem><para> | |
567 | Window information (window IDs and clipping information for each | |
568 | back-end window that corresponds to each DMX window) | |
569 | </para></listitem> | |
570 | <listitem><para> | |
571 | Input device information (mappings from DMX device IDs to | |
572 | back-end device IDs) | |
573 | </para></listitem> | |
574 | <listitem><para> | |
575 | Force window creation (so that a client can override the | |
576 | server-side lazy window creation optimization) | |
577 | </para></listitem> | |
578 | <listitem><para> | |
579 | Reconfiguration (so that a client can request that a screen | |
580 | position be changed) | |
581 | </para></listitem> | |
582 | <listitem><para> | |
583 | Addition and removal of back-end servers and back-end and | |
584 | console inputs. | |
585 | </para></listitem> | |
586 | </orderedlist> | |
587 | </para> | |
588 | <!-- September 2002; July 2003 --> | |
589 | ||
590 | </sect2> | |
591 | ||
592 | <sect2> | |
593 | <title>Common X extension support</title> | |
594 | ||
595 | <para>The XInput, XKeyboard and Shape extensions are commonly used | |
596 | extensions to the base X11 protocol. XInput allows multiple and | |
597 | non-standard input devices to be accessed simultaneously. These input | |
598 | devices can be connected to either the front-end or back-end servers. | |
599 | XKeyboard allows much better keyboard mappings control. Shape adds | |
600 | support for arbitrarily shaped windows and is used by various window | |
601 | managers. Nearly all potential back-end X servers make these extensions | |
602 | available, and support for each one will be added to the DMX system. | |
603 | </para> | |
604 | ||
605 | <para>In addition to the extensions listed above, support for the X | |
606 | Rendering extension (Render) is being developed. Render adds digital | |
607 | image composition to the rendering model used by the X Window System. | |
608 | While this extension is still under development by Keith Packard of HP, | |
609 | support for the current version will be added to the DMX system. | |
610 | </para> | |
611 | ||
612 | <para>Support for the XTest extension was added during the first | |
613 | development phase. | |
614 | </para> | |
615 | ||
616 | <!-- WARNING: this list is duplicated in the Phase IV discussion --> | |
617 | <para>Status: The following extensions are supported and are discussed in | |
618 | more detail in Phase IV of the Development Results (see appendix): | |
619 | BIG-REQUESTS, | |
620 | DEC-XTRAP, | |
621 | DMX, | |
622 | DPMS, | |
623 | Extended-Visual-Information, | |
624 | GLX, | |
625 | LBX, | |
626 | RECORD, | |
627 | RENDER, | |
628 | SECURITY, | |
629 | SHAPE, | |
630 | SYNC, | |
631 | X-Resource, | |
632 | XC-APPGROUP, | |
633 | XC-MISC, | |
634 | XFree86-Bigfont, | |
635 | XINERAMA, | |
636 | XInputExtension, | |
637 | XKEYBOARD, and | |
638 | XTEST. | |
639 | <!-- November 2002; updated February 2003, July 2003 --> | |
640 | </para> | |
641 | </sect2> | |
642 | ||
643 | <sect2> | |
644 | <title>OpenGL support</title> | |
645 | ||
646 | <para>OpenGL support using the Mesa code base exists in XFree86 release 4 | |
647 | and later. Currently, the direct rendering infrastructure (DRI) | |
648 | provides accelerated OpenGL support for local clients and unaccelerated | |
649 | OpenGL support (i.e., software rendering) is provided for non-local | |
650 | clients. | |
651 | </para> | |
652 | ||
653 | <para>The single head OpenGL support in XFree86 4.x will be extended to use | |
654 | the DMX system. When the front and back-end servers are on the same | |
655 | physical hardware, it is possible to use the DRI to directly render to | |
656 | the back-end servers. First, the existing DRI will be extended to | |
657 | support multiple display heads, and then to support the DMX system. | |
658 | OpenGL rendering requests will be direct rendering to each back-end X | |
659 | server. The DRI will request the screen layout (either from the | |
660 | existing Xinerama extension or a DMX-specific extension). Support for | |
661 | synchronized swap buffers will also be added (on hardware that supports | |
662 | it). Note that a single front-end server with a single back-end server | |
663 | on the same physical machine can emulate accelerated indirect rendering. | |
664 | </para> | |
665 | ||
666 | <para>When the front and back-end servers are on different physical | |
667 | hardware or are using non-XFree86 4.x X servers, a mechanism to render | |
668 | primitives across the back-end servers will be provided. There are | |
669 | several options as to how this can be implemented. | |
670 | </para> | |
671 | ||
672 | <orderedlist> | |
673 | <listitem> | |
674 | <para>The existing OpenGL support in each back-end server can be | |
675 | used by repackaging rendering primitives and sending them to each | |
676 | back-end server. This option is similar to the unoptimized | |
677 | Xnest-style approach mentioned above. Optimization of this solution | |
678 | is beyond the scope of this project and is better suited to other | |
679 | distributed rendering systems. | |
680 | </para></listitem> | |
681 | ||
682 | <listitem> | |
683 | <para>Rendering to a pixmap in the front-end server using the | |
684 | current XFree86 4.x code, and then displaying to the back-ends via | |
685 | calls to XPutImage() is another option. This option is similar to | |
686 | the shadow frame buffer approach mentioned above. It is slower and | |
687 | bandwidth intensive, but has the advantage that the back-end servers | |
688 | are not required to have OpenGL support. | |
689 | </para></listitem> | |
690 | </orderedlist> | |
691 | ||
692 | <para>These, and other, options will be investigated in this phase of the | |
693 | work. | |
694 | </para> | |
695 | ||
696 | <para>Work by others have made Chromium DMX-aware. Chromium will use the | |
697 | DMX X protocol extension to obtain information about the back-end | |
698 | servers and will render directly to those servers, bypassing DMX. | |
699 | </para> | |
700 | ||
701 | <para>Status: OpenGL support by the glxProxy extension was implemented by | |
702 | SGI and has been integrated into the DMX code base. | |
703 | </para> | |
704 | <!-- May 2003--> | |
705 | </sect2> | |
706 | ||
707 | </sect1> | |
708 | ||
709 | <!-- ============================================================ --> | |
710 | <sect1> | |
711 | <title>Current issues</title> | |
712 | ||
713 | <para>In this sections the current issues are outlined that require further | |
714 | investigation. | |
715 | </para> | |
716 | ||
717 | <sect2> | |
718 | <title>Fonts</title> | |
719 | ||
720 | <para>The font path and glyphs need to be the same for the front-end and | |
721 | each of the back-end servers. Font glyphs could be sent to the back-end | |
722 | servers as necessary but this would consume a significant amount of | |
723 | available bandwidth during font rendering for clients that use many | |
724 | different fonts (e.g., Netscape). Initially, the font server (xfs) will | |
725 | be used to provide the fonts to both the front-end and back-end servers. | |
726 | Other possibilities will be investigated during development. | |
727 | </para> | |
728 | </sect2> | |
729 | ||
730 | <sect2> | |
731 | <title>Zero width rendering primitives</title> | |
732 | ||
733 | <para>To allow pixmap and on-screen rendering to be pixel perfect, all | |
734 | back-end servers must render zero width primitives exactly the same as | |
735 | the front-end renders the primitives to pixmaps. For those back-end | |
736 | servers that do not exactly match, zero width primitives will be | |
737 | automatically converted to one width primitives. This can be handled in | |
738 | the front-end server via the GC state. | |
739 | </para> | |
740 | </sect2> | |
741 | ||
742 | <sect2> | |
743 | <title>Output scaling</title> | |
744 | ||
745 | <para>With very large tiled displays, it might be difficult to read the | |
746 | information on the standard X desktop. In particular, the cursor can be | |
747 | easily lost and fonts could be difficult to read. Automatic primitive | |
748 | scaling might prove to be very useful. We will investigate the | |
749 | possibility of scaling the cursor and providing a set of alternate | |
750 | pre-scaled fonts to replace the standard fonts that many applications | |
751 | use (e.g., fixed). Other options for automatic scaling will also be | |
752 | investigated. | |
753 | </para> | |
754 | </sect2> | |
755 | ||
756 | <sect2> | |
757 | <title>Per-screen colormaps</title> | |
758 | ||
759 | <para>Each screen's default colormap in the set of back-end X servers | |
760 | should be able to be adjusted via a configuration utility. This support | |
761 | is would allow the back-end screens to be calibrated via custom gamma | |
762 | tables. On 24-bit systems that support a DirectColor visual, this type | |
763 | of correction can be accommodated. One possible implementation would be | |
764 | to advertise to X client of the DMX server a TrueColor visual while | |
765 | using DirectColor visuals on the back-end servers to implement this type | |
766 | of color correction. Other options will be investigated. | |
767 | </para> | |
768 | </sect2> | |
769 | </sect1> | |
770 | ||
771 | <!-- ============================================================ --> | |
772 | <appendix> | |
773 | <title>Appendix</title> | |
774 | ||
775 | <sect1> | |
776 | <title>Background</title> | |
777 | ||
778 | <para>This section describes the existing Open Source architectures that | |
779 | can be used to handle multiple screens and upon which this development | |
780 | project is based. This section was written before the implementation | |
781 | was finished, and may not reflect actual details of the implementation. | |
782 | It is left for historical interest only. | |
783 | </para> | |
784 | ||
785 | <sect2> | |
786 | <title>Core input device handling</title> | |
787 | ||
788 | <para>The following is a description of how core input devices are handled | |
789 | by an X server. | |
790 | </para> | |
791 | ||
792 | <sect3> | |
793 | <title>InitInput()</title> | |
794 | ||
795 | <para>InitInput() is a DDX function that is called at the start of each | |
796 | server generation from the X server's main() function. Its purpose is | |
797 | to determine what input devices are connected to the X server, register | |
798 | them with the DIX and MI layers, and initialize the input event queue. | |
799 | InitInput() does not have a return value, but the X server will abort if | |
800 | either a core keyboard device or a core pointer device are not | |
801 | registered. Extended input (XInput) devices can also be registered in | |
802 | InitInput(). | |
803 | </para> | |
804 | ||
805 | <para>InitInput() usually has implementation specific code to determine | |
806 | which input devices are available. For each input device it will be | |
807 | using, it calls AddInputDevice(): | |
808 | ||
809 | <variablelist> | |
810 | <varlistentry> | |
811 | <term>AddInputDevice()</term> | |
812 | <listitem><para>This DIX function allocates the device structure, | |
813 | registers a callback function (which handles device init, close, on and | |
814 | off), and returns the input handle, which can be treated as opaque. It | |
815 | is called once for each input device. | |
816 | </para></listitem> | |
817 | </varlistentry> | |
818 | </variablelist> | |
819 | </para> | |
820 | ||
821 | <para>Once input handles for core keyboard and core pointer devices have | |
822 | been obtained from AddInputDevice(). If both core devices are not | |
823 | registered, then the X server will exit with a fatal error when it | |
824 | attempts to start the input devices in InitAndStartDevices(), which is | |
825 | called directly after InitInput() (see below). | |
826 | </para> | |
827 | ||
828 | <para>The core pointer device is then registered with the miPointer code | |
829 | (which does the high level cursor handling). While this registration | |
830 | is not necessary for correct miPointer operation in the current XFree86 | |
831 | code, it is still done mostly for compatibility reasons. | |
832 | </para> | |
833 | ||
834 | <para><variablelist> | |
835 | ||
836 | <varlistentry> | |
837 | <term>miRegisterPointerDevice()</term> | |
838 | <listitem><para>This MI function registers the core | |
839 | pointer's input handle with with the miPointer code. | |
840 | </para></listitem></varlistentry> | |
841 | </variablelist> | |
842 | </para> | |
843 | ||
844 | <para>The final part of InitInput() is the initialization of the input | |
845 | event queue handling. In most cases, the event queue handling provided | |
846 | in the MI layer is used. The primary XFree86 X server uses its own | |
847 | event queue handling to support some special cases related to the XInput | |
848 | extension and the XFree86-specific DGA extension. For our purposes, the | |
849 | MI event queue handling should be suitable. It is initialized by | |
850 | calling mieqInit(): | |
851 | ||
852 | <variablelist> | |
853 | <varlistentry> | |
854 | <term>mieqInit()</term> | |
855 | <listitem><para>This MI function initializes the MI event queue for the | |
856 | core devices, and is passed the public component of the input handles | |
857 | for the two core devices. | |
858 | </para></listitem></varlistentry> | |
859 | </variablelist> | |
860 | </para> | |
861 | ||
862 | <para>If a wakeup handler is required to deliver synchronous input | |
863 | events, it can be registered here by calling the DIX function | |
864 | RegisterBlockAndWakeupHandlers(). (See the devReadInput() description | |
865 | below.) | |
866 | </para> | |
867 | </sect3> | |
868 | ||
869 | <sect3> | |
870 | <title>InitAndStartDevices()</title> | |
871 | ||
872 | <para>InitAndStartDevices() is a DIX function that is called immediately | |
873 | after InitInput() from the X server's main() function. Its purpose is | |
874 | to initialize each input device that was registered with | |
875 | AddInputDevice(), enable each input device that was successfully | |
876 | initialized, and create the list of enabled input devices. Once each | |
877 | registered device is processed in this way, the list of enabled input | |
878 | devices is checked to make sure that both a core keyboard device and | |
879 | core pointer device were registered and successfully enabled. If not, | |
880 | InitAndStartDevices() returns failure, and results in the the X server | |
881 | exiting with a fatal error. | |
882 | </para> | |
883 | ||
884 | <para>Each registered device is initialized by calling its callback | |
885 | (dev->deviceProc) with the DEVICE_INIT argument: | |
886 | ||
887 | <variablelist> | |
888 | <varlistentry> | |
889 | <term>(*dev->deviceProc)(dev, DEVICE_INIT)</term> | |
890 | <listitem> | |
891 | <para>This function initializes the | |
892 | device structs with core information relevant to the device. | |
893 | </para> | |
894 | ||
895 | <para>For pointer devices, this means specifying the number of buttons, | |
896 | default button mapping, the function used to get motion events (usually | |
897 | miPointerGetMotionEvents()), the function used to change/control the | |
898 | core pointer motion parameters (acceleration and threshold), and the | |
899 | motion buffer size. | |
900 | </para> | |
901 | ||
902 | <para>For keyboard devices, this means specifying the keycode range, | |
903 | default keycode to keysym mapping, default modifier mapping, and the | |
904 | functions used to sound the keyboard bell and modify/control the | |
905 | keyboard parameters (LEDs, bell pitch and duration, key click, which | |
906 | keys are auto-repeating, etc). | |
907 | </para></listitem></varlistentry> | |
908 | </variablelist> | |
909 | </para> | |
910 | ||
911 | <para>Each initialized device is enabled by calling EnableDevice(): | |
912 | ||
913 | <variablelist> | |
914 | <varlistentry> | |
915 | <term>EnableDevice()</term> | |
916 | <listitem> | |
917 | <para>EnableDevice() calls the device callback with | |
918 | DEVICE_ON: | |
919 | <variablelist> | |
920 | <varlistentry> | |
921 | <term>(*dev->deviceProc)(dev, DEVICE_ON)</term> | |
922 | <listitem> | |
923 | <para>This typically opens and | |
924 | initializes the relevant physical device, and when appropriate, | |
925 | registers the device's file descriptor (or equivalent) as a valid | |
926 | input source. | |
927 | </para></listitem></varlistentry> | |
928 | </variablelist> | |
929 | </para> | |
930 | ||
931 | <para>EnableDevice() then adds the device handle to the X server's | |
932 | global list of enabled devices. | |
933 | </para></listitem></varlistentry> | |
934 | </variablelist> | |
935 | </para> | |
936 | ||
937 | <para>InitAndStartDevices() then verifies that a valid core keyboard and | |
938 | pointer has been initialized and enabled. It returns failure if either | |
939 | are missing. | |
940 | </para> | |
941 | </sect3> | |
942 | ||
943 | <sect3> | |
944 | <title>devReadInput()</title> | |
945 | ||
946 | <para>Each device will have some function that gets called to read its | |
947 | physical input. These may be called in a number of different ways. In | |
948 | the case of synchronous I/O, they will be called from a DDX | |
949 | wakeup-handler that gets called after the server detects that new input is | |
950 | available. In the case of asynchronous I/O, they will be called from a | |
951 | (SIGIO) signal handler triggered when new input is available. This | |
952 | function should do at least two things: make sure that input events get | |
953 | enqueued, and make sure that the cursor gets moved for motion events | |
954 | (except if these are handled later by the driver's own event queue | |
955 | processing function, which cannot be done when using the MI event queue | |
956 | handling). | |
957 | </para> | |
958 | ||
959 | <para>Events are queued by calling mieqEnqueue(): | |
960 | ||
961 | <variablelist> | |
962 | <varlistentry> | |
963 | <term>mieqEnqueue()</term> | |
964 | <listitem> | |
965 | <para>This MI function is used to add input events to the | |
966 | event queue. It is simply passed the event to be queued. | |
967 | </para></listitem></varlistentry> | |
968 | </variablelist> | |
969 | </para> | |
970 | ||
971 | <para>The cursor position should be updated when motion events are | |
972 | enqueued by calling miPointerDeltaCursor(): | |
973 | ||
974 | <variablelist> | |
975 | <varlistentry> | |
976 | <term>miPointerDeltaCursor()</term> | |
977 | <listitem> | |
978 | <para>This MI function is used to move the cursor | |
979 | relative to its current position. | |
980 | </para></listitem></varlistentry> | |
981 | </variablelist> | |
982 | </para> | |
983 | </sect3> | |
984 | ||
985 | <sect3> | |
986 | <title>ProcessInputEvents()</title> | |
987 | ||
988 | <para>ProcessInputEvents() is a DDX function that is called from the X | |
989 | server's main dispatch loop when new events are available in the input | |
990 | event queue. It typically processes the enqueued events, and updates | |
991 | the cursor/pointer position. It may also do other DDX-specific event | |
992 | processing. | |
993 | </para> | |
994 | ||
995 | <para>Enqueued events are processed by mieqProcessInputEvents() and passed | |
996 | to the DIX layer for transmission to clients: | |
997 | ||
998 | <variablelist> | |
999 | <varlistentry> | |
1000 | <term>mieqProcessInputEvents()</term> | |
1001 | <listitem> | |
1002 | <para>This function processes each event in the | |
1003 | event queue, and passes it to the device's input processing function. | |
1004 | The DIX layer provides default functions to do this processing, and they | |
1005 | handle the task of getting the events passed back to the relevant | |
1006 | clients. | |
1007 | </para></listitem></varlistentry> | |
1008 | <varlistentry> | |
1009 | <term>miPointerUpdate()</term> | |
1010 | <listitem> | |
1011 | <para>This function resynchronized the cursor position | |
1012 | with the new pointer position. It also takes care of moving the cursor | |
1013 | between screens when needed in multi-head configurations. | |
1014 | </para></listitem></varlistentry> | |
1015 | </variablelist> | |
1016 | </para> | |
1017 | ||
1018 | </sect3> | |
1019 | ||
1020 | <sect3> | |
1021 | <title>DisableDevice()</title> | |
1022 | ||
1023 | <para>DisableDevice is a DIX function that removes an input device from the | |
1024 | list of enabled devices. The result of this is that the device no | |
1025 | longer generates input events. The device's data structures are kept in | |
1026 | place, and disabling a device like this can be reversed by calling | |
1027 | EnableDevice(). DisableDevice() may be called from the DDX when it is | |
1028 | desirable to do so (e.g., the XFree86 server does this when VT | |
1029 | switching). Except for special cases, this is not normally called for | |
1030 | core input devices. | |
1031 | </para> | |
1032 | ||
1033 | <para>DisableDevice() calls the device's callback function with | |
1034 | <constant>DEVICE_OFF</constant>: | |
1035 | ||
1036 | <variablelist> | |
1037 | <varlistentry> | |
1038 | <term>(*dev->deviceProc)(dev, DEVICE_OFF)</term> | |
1039 | <listitem> | |
1040 | <para>This typically closes the | |
1041 | relevant physical device, and when appropriate, unregisters the device's | |
1042 | file descriptor (or equivalent) as a valid input source. | |
1043 | </para></listitem></varlistentry> | |
1044 | </variablelist> | |
1045 | </para> | |
1046 | ||
1047 | <para>DisableDevice() then removes the device handle from the X server's | |
1048 | global list of enabled devices. | |
1049 | </para> | |
1050 | ||
1051 | </sect3> | |
1052 | ||
1053 | <sect3> | |
1054 | <title>CloseDevice()</title> | |
1055 | ||
1056 | <para>CloseDevice is a DIX function that removes an input device from the | |
1057 | list of available devices. It disables input from the device and frees | |
1058 | all data structures associated with the device. This function is | |
1059 | usually called from CloseDownDevices(), which is called from main() at | |
1060 | the end of each server generation to close all input devices. | |
1061 | </para> | |
1062 | ||
1063 | <para>CloseDevice() calls the device's callback function with | |
1064 | <constant>DEVICE_CLOSE</constant>: | |
1065 | ||
1066 | <variablelist> | |
1067 | <varlistentry> | |
1068 | <term>(*dev->deviceProc)(dev, DEVICE_CLOSE)</term> | |
1069 | <listitem> | |
1070 | <para>This typically closes the | |
1071 | relevant physical device, and when appropriate, unregisters the device's | |
1072 | file descriptor (or equivalent) as a valid input source. If any device | |
1073 | specific data structures were allocated when the device was initialized, | |
1074 | they are freed here. | |
1075 | </para></listitem></varlistentry> | |
1076 | </variablelist> | |
1077 | </para> | |
1078 | ||
1079 | <para>CloseDevice() then frees the data structures that were allocated | |
1080 | for the device when it was registered/initialized. | |
1081 | </para> | |
1082 | ||
1083 | </sect3> | |
1084 | ||
1085 | <sect3> | |
1086 | <title>LegalModifier()</title> | |
1087 | <!-- dmx/dmxinput.c - currently returns TRUE --> | |
1088 | <para>LegalModifier() is a required DDX function that can be used to | |
1089 | restrict which keys may be modifier keys. This seems to be present for | |
1090 | historical reasons, so this function should simply return TRUE | |
1091 | unconditionally. | |
1092 | </para> | |
1093 | ||
1094 | </sect3> | |
1095 | </sect2> | |
1096 | ||
1097 | <sect2> | |
1098 | <title>Output handling</title> | |
1099 | ||
1100 | <para>The following sections describe the main functions required to | |
1101 | initialize, use and close the output device(s) for each screen in the X | |
1102 | server. | |
1103 | </para> | |
1104 | ||
1105 | <sect3> | |
1106 | <title>InitOutput()</title> | |
1107 | ||
1108 | <para>This DDX function is called near the start of each server generation | |
1109 | from the X server's main() function. InitOutput()'s main purpose is to | |
1110 | initialize each screen and fill in the global screenInfo structure for | |
1111 | each screen. It is passed three arguments: a pointer to the screenInfo | |
1112 | struct, which it is to initialize, and argc and argv from main(), which | |
1113 | can be used to determine additional configuration information. | |
1114 | </para> | |
1115 | ||
1116 | <para>The primary tasks for this function are outlined below: | |
1117 | ||
1118 | <orderedlist> | |
1119 | <listitem> | |
1120 | <para><emphasis remap="bf">Parse configuration info:</emphasis> The first task of InitOutput() | |
1121 | is to parses any configuration information from the configuration | |
1122 | file. In addition to the XF86Config file, other configuration | |
1123 | information can be taken from the command line. The command line | |
1124 | options can be gathered either in InitOutput() or earlier in the | |
1125 | ddxProcessArgument() function, which is called by | |
1126 | ProcessCommandLine(). The configuration information determines the | |
1127 | characteristics of the screen(s). For example, in the XFree86 X | |
1128 | server, the XF86Config file specifies the monitor information, the | |
1129 | screen resolution, the graphics devices and slots in which they are | |
1130 | located, and, for Xinerama, the screens' layout. | |
1131 | </para> | |
1132 | </listitem> | |
1133 | ||
1134 | <listitem> | |
1135 | <para><emphasis remap="bf">Initialize screen info:</emphasis> The next task is to initialize | |
1136 | the screen-dependent internal data structures. For example, part of | |
1137 | what the XFree86 X server does is to allocate its screen and pixmap | |
1138 | private indices, probe for graphics devices, compare the probed | |
1139 | devices to the ones listed in the XF86Config file, and add the ones that | |
1140 | match to the internal xf86Screens[] structure. | |
1141 | </para> | |
1142 | </listitem> | |
1143 | ||
1144 | <listitem> | |
1145 | <para><emphasis remap="bf">Set pixmap formats:</emphasis> The next task is to initialize the | |
1146 | screenInfo's image byte order, bitmap bit order and bitmap scanline | |
1147 | unit/pad. The screenInfo's pixmap format's depth, bits per pixel | |
1148 | and scanline padding is also initialized at this stage. | |
1149 | </para> | |
1150 | </listitem> | |
1151 | ||
1152 | <listitem> | |
1153 | <para><emphasis remap="bf">Unify screen info:</emphasis> An optional task that might be done at | |
1154 | this stage is to compare all of the information from the various | |
1155 | screens and determines if they are compatible (i.e., if the set of | |
1156 | screens can be unified into a single desktop). This task has | |
1157 | potential to be useful to the DMX front-end server, if Xinerama's | |
1158 | PanoramiXConsolidate() function is not sufficient. | |
1159 | </para> | |
1160 | </listitem> | |
1161 | </orderedlist> | |
1162 | </para> | |
1163 | ||
1164 | <para>Once these tasks are complete, the valid screens are known and each | |
1165 | of these screens can be initialized by calling AddScreen(). | |
1166 | </para> | |
1167 | </sect3> | |
1168 | ||
1169 | <sect3> | |
1170 | <title>AddScreen()</title> | |
1171 | ||
1172 | <para>This DIX function is called from InitOutput(), in the DDX layer, to | |
1173 | add each new screen to the screenInfo structure. The DDX screen | |
1174 | initialization function and command line arguments (i.e., argc and argv) | |
1175 | are passed to it as arguments. | |
1176 | </para> | |
1177 | ||
1178 | <para>This function first allocates a new Screen structure and any privates | |
1179 | that are required. It then initializes some of the fields in the Screen | |
1180 | struct and sets up the pixmap padding information. Finally, it calls | |
1181 | the DDX screen initialization function ScreenInit(), which is described | |
1182 | below. It returns the number of the screen that were just added, or -1 | |
1183 | if there is insufficient memory to add the screen or if the DDX screen | |
1184 | initialization fails. | |
1185 | </para> | |
1186 | </sect3> | |
1187 | ||
1188 | <sect3> | |
1189 | <title>ScreenInit()</title> | |
1190 | ||
1191 | <para>This DDX function initializes the rest of the Screen structure with | |
1192 | either generic or screen-specific functions (as necessary). It also | |
1193 | fills in various screen attributes (e.g., width and height in | |
1194 | millimeters, black and white pixel values). | |
1195 | </para> | |
1196 | ||
1197 | <para>The screen init function usually calls several functions to perform | |
1198 | certain screen initialization functions. They are described below: | |
1199 | ||
1200 | <variablelist> | |
1201 | <varlistentry> | |
1202 | <term>{mi,*fb}ScreenInit()</term> | |
1203 | <listitem> | |
1204 | <para>The DDX layer's ScreenInit() function usually | |
1205 | calls another layer's ScreenInit() function (e.g., miScreenInit() or | |
1206 | fbScreenInit()) to initialize the fallbacks that the DDX driver does not | |
1207 | specifically handle. | |
1208 | </para> | |
1209 | ||
1210 | <para>After calling another layer's ScreenInit() function, any | |
1211 | screen-specific functions either wrap or replace the other layer's | |
1212 | function pointers. If a function is to be wrapped, each of the old | |
1213 | function pointers from the other layer are stored in a screen private | |
1214 | area. Common functions to wrap are CloseScreen() and SaveScreen(). | |
1215 | </para></listitem></varlistentry> | |
1216 | ||
1217 | <varlistentry> | |
1218 | <term>miDCInitialize()</term> | |
1219 | <listitem> | |
1220 | <para>This MI function initializes the MI cursor | |
1221 | display structures and function pointers. If a hardware cursor is used, | |
1222 | the DDX layer's ScreenInit() function will wrap additional screen and | |
1223 | the MI cursor display function pointers. | |
1224 | </para></listitem></varlistentry> | |
1225 | </variablelist> | |
1226 | </para> | |
1227 | ||
1228 | <para>Another common task for ScreenInit() function is to initialize the | |
1229 | output device state. For example, in the XFree86 X server, the | |
1230 | ScreenInit() function saves the original state of the video card and | |
1231 | then initializes the video mode of the graphics device. | |
1232 | </para> | |
1233 | </sect3> | |
1234 | ||
1235 | <sect3> | |
1236 | <title>CloseScreen()</title> | |
1237 | ||
1238 | <para>This function restores any wrapped screen functions (and in | |
1239 | particular the wrapped CloseScreen() function) and restores the state of | |
1240 | the output device to its original state. It should also free any | |
1241 | private data it created during the screen initialization. | |
1242 | </para> | |
1243 | </sect3> | |
1244 | ||
1245 | <sect3> | |
1246 | <title>GC operations</title> | |
1247 | ||
1248 | <para>When the X server is requested to render drawing primitives, it does | |
1249 | so by calling drawing functions through the graphics context's operation | |
1250 | function pointer table (i.e., the GCOps functions). These functions | |
1251 | render the basic graphics operations such as drawing rectangles, lines, | |
1252 | text or copying pixmaps. Default routines are provided either by the MI | |
1253 | layer, which draws indirectly through a simple span interface, or by the | |
1254 | framebuffer layers (e.g., CFB, MFB, FB), which draw directly to a | |
1255 | linearly mapped frame buffer. | |
1256 | </para> | |
1257 | ||
1258 | <para>To take advantage of special hardware on the graphics device, | |
1259 | specific GCOps functions can be replaced by device specific code. | |
1260 | However, many times the graphics devices can handle only a subset of the | |
1261 | possible states of the GC, so during graphics context validation, | |
1262 | appropriate routines are selected based on the state and capabilities of | |
1263 | the hardware. For example, some graphics hardware can accelerate single | |
1264 | pixel width lines with certain dash patterns. Thus, for dash patterns | |
1265 | that are not supported by hardware or for width 2 or greater lines, the | |
1266 | default routine is chosen during GC validation. | |
1267 | </para> | |
1268 | ||
1269 | <para>Note that some pointers to functions that draw to the screen are | |
1270 | stored in the Screen structure. They include GetImage(), GetSpans(), | |
1271 | CopyWindow() and RestoreAreas(). | |
1272 | </para> | |
1273 | </sect3> | |
1274 | ||
1275 | <sect3> | |
1276 | <title>Xnest</title> | |
1277 | ||
1278 | <para>The Xnest X server is a special proxy X server that relays the X | |
1279 | protocol requests that it receives to a ``real'' X server that then | |
1280 | processes the requests and displays the results, if applicable. To the X | |
1281 | applications, Xnest appears as if it is a regular X server. However, | |
1282 | Xnest is both server to the X application and client of the real X | |
1283 | server, which will actually handle the requests. | |
1284 | </para> | |
1285 | ||
1286 | <para>The Xnest server implements all of the standard input and output | |
1287 | initialization steps outlined above. | |
1288 | </para> | |
1289 | ||
1290 | <para><variablelist> | |
1291 | <varlistentry> | |
1292 | <term>InitOutput()</term> | |
1293 | <listitem> | |
1294 | <para>Xnest takes its configuration information from | |
1295 | command line arguments via ddxProcessArguments(). This information | |
1296 | includes the real X server display to connect to, its default visual | |
1297 | class, the screen depth, the Xnest window's geometry, etc. Xnest then | |
1298 | connects to the real X server and gathers visual, colormap, depth and | |
1299 | pixmap information about that server's display, creates a window on that | |
1300 | server, which will be used as the root window for Xnest. | |
1301 | </para> | |
1302 | ||
1303 | <para>Next, Xnest initializes its internal data structures and uses the | |
1304 | data from the real X server's pixmaps to initialize its own pixmap | |
1305 | formats. Finally, it calls AddScreen(xnestOpenScreen, argc, argv) to | |
1306 | initialize each of its screens. | |
1307 | </para></listitem></varlistentry> | |
1308 | ||
1309 | <varlistentry> | |
1310 | <term>ScreenInit()</term> | |
1311 | <listitem> | |
1312 | <para>Xnest's ScreenInit() function is called | |
1313 | xnestOpenScreen(). This function initializes its screen's depth and | |
1314 | visual information, and then calls miScreenInit() to set up the default | |
1315 | screen functions. It then calls miDCInitialize() to initialize the | |
1316 | software cursor. | |
1317 | Finally, it replaces many of the screen functions with its own | |
1318 | functions that repackage and send the requests to the real X server to | |
1319 | which Xnest is attached. | |
1320 | </para></listitem></varlistentry> | |
1321 | ||
1322 | <varlistentry> | |
1323 | <term>CloseScreen()</term> | |
1324 | <listitem> | |
1325 | <para>This function frees its internal data structure | |
1326 | allocations. Since it replaces instead of wrapping screen functions, | |
1327 | there are no function pointers to unwrap. This can potentially lead to | |
1328 | problems during server regeneration. | |
1329 | </para></listitem></varlistentry> | |
1330 | ||
1331 | <varlistentry> | |
1332 | <term>GC operations</term> | |
1333 | <listitem> | |
1334 | <para>The GC operations in Xnest are very simple since | |
1335 | they leave all of the drawing to the real X server to which Xnest is | |
1336 | attached. Each of the GCOps takes the request and sends it to the | |
1337 | real X server using standard Xlib calls. For example, the X | |
1338 | application issues a XDrawLines() call. This function turns into a | |
1339 | protocol request to Xnest, which calls the xnestPolylines() function | |
1340 | through Xnest's GCOps function pointer table. The xnestPolylines() | |
1341 | function is only a single line, which calls XDrawLines() using the same | |
1342 | arguments that were passed into it. Other GCOps functions are very | |
1343 | similar. Two exceptions to the simple GCOps functions described above | |
1344 | are the image functions and the BLT operations. | |
1345 | </para> | |
1346 | ||
1347 | <para>The image functions, GetImage() and PutImage(), must use a temporary | |
1348 | image to hold the image to be put of the image that was just grabbed | |
1349 | from the screen while it is in transit to the real X server or the | |
1350 | client. When the image has been transmitted, the temporary image is | |
1351 | destroyed. | |
1352 | </para> | |
1353 | ||
1354 | <para>The BLT operations, CopyArea() and CopyPlane(), handle not only the | |
1355 | copy function, which is the same as the simple cases described above, | |
1356 | but also the graphics exposures that result when the GC's graphics | |
1357 | exposure bit is set to True. Graphics exposures are handled in a helper | |
1358 | function, xnestBitBlitHelper(). This function collects the exposure | |
1359 | events from the real X server and, if any resulting in regions being | |
1360 | exposed, then those regions are passed back to the MI layer so that it | |
1361 | can generate exposure events for the X application. | |
1362 | </para></listitem></varlistentry> | |
1363 | </variablelist> | |
1364 | </para> | |
1365 | ||
1366 | <para>The Xnest server takes its input from the X server to which it is | |
1367 | connected. When the mouse is in the Xnest server's window, keyboard and | |
1368 | mouse events are received by the Xnest server, repackaged and sent back | |
1369 | to any client that requests those events. | |
1370 | </para> | |
1371 | </sect3> | |
1372 | ||
1373 | <sect3> | |
1374 | <title>Shadow framebuffer</title> | |
1375 | ||
1376 | <para>The most common type of framebuffer is a linear array memory that | |
1377 | maps to the video memory on the graphics device. However, accessing | |
1378 | that video memory over an I/O bus (e.g., ISA or PCI) can be slow. The | |
1379 | shadow framebuffer layer allows the developer to keep the entire | |
1380 | framebuffer in main memory and copy it back to video memory at regular | |
1381 | intervals. It also has been extended to handle planar video memory and | |
1382 | rotated framebuffers. | |
1383 | </para> | |
1384 | ||
1385 | <para>There are two main entry points to the shadow framebuffer code: | |
1386 | ||
1387 | <variablelist> | |
1388 | <varlistentry> | |
1389 | <term>shadowAlloc(width, height, bpp)</term> | |
1390 | <listitem> | |
1391 | <para>This function allocates the in | |
1392 | memory copy of the framebuffer of size width*height*bpp. It returns a | |
1393 | pointer to that memory, which will be used by the framebuffer | |
1394 | ScreenInit() code during the screen's initialization. | |
1395 | </para></listitem></varlistentry> | |
1396 | ||
1397 | <varlistentry> | |
1398 | <term>shadowInit(pScreen, updateProc, windowProc)</term> | |
1399 | <listitem> | |
1400 | <para>This function | |
1401 | initializes the shadow framebuffer layer. It wraps several screen | |
1402 | drawing functions, and registers a block handler that will update the | |
1403 | screen. The updateProc is a function that will copy the damaged regions | |
1404 | to the screen, and the windowProc is a function that is used when the | |
1405 | entire linear video memory range cannot be accessed simultaneously so | |
1406 | that only a window into that memory is available (e.g., when using the | |
1407 | VGA aperture). | |
1408 | </para></listitem></varlistentry> | |
1409 | </variablelist> | |
1410 | </para> | |
1411 | ||
1412 | <para>The shadow framebuffer code keeps track of the damaged area of each | |
1413 | screen by calculating the bounding box of all drawing operations that | |
1414 | have occurred since the last screen update. Then, when the block handler | |
1415 | is next called, only the damaged portion of the screen is updated. | |
1416 | </para> | |
1417 | ||
1418 | <para>Note that since the shadow framebuffer is kept in main memory, all | |
1419 | drawing operations are performed by the CPU and, thus, no accelerated | |
1420 | hardware drawing operations are possible. | |
1421 | </para> | |
1422 | ||
1423 | </sect3> | |
1424 | </sect2> | |
1425 | ||
1426 | <sect2> | |
1427 | <title>Xinerama</title> | |
1428 | ||
1429 | <para>Xinerama is an X extension that allows multiple physical screens | |
1430 | controlled by a single X server to appear as a single screen. Although | |
1431 | the extension allows clients to find the physical screen layout via | |
1432 | extension requests, it is completely transparent to clients at the core | |
1433 | X11 protocol level. The original public implementation of Xinerama came | |
1434 | from Digital/Compaq. XFree86 rewrote it, filling in some missing pieces | |
1435 | and improving both X11 core protocol compliance and performance. The | |
1436 | Xinerama extension will be passing through X.Org's standardization | |
1437 | process in the near future, and the sample implementation will be based | |
1438 | on this rewritten version. | |
1439 | </para> | |
1440 | ||
1441 | <para>The current implementation of Xinerama is based primarily in the DIX | |
1442 | (device independent) and MI (machine independent) layers of the X | |
1443 | server. With few exceptions the DDX layers do not need any changes to | |
1444 | support Xinerama. X server extensions often do need modifications to | |
1445 | provide full Xinerama functionality. | |
1446 | </para> | |
1447 | ||
1448 | <para>The following is a code-level description of how Xinerama functions. | |
1449 | </para> | |
1450 | ||
1451 | <para>Note: Because the Xinerama extension was originally called the | |
1452 | PanoramiX extension, many of the Xinerama functions still have the | |
1453 | PanoramiX prefix. | |
1454 | </para> | |
1455 | ||
1456 | <variablelist> | |
1457 | <varlistentry> | |
1458 | <term>PanoramiXExtensionInit()</term> | |
1459 | <listitem> | |
1460 | <para>PanoramiXExtensionInit() is a | |
1461 | device-independent extension function that is called at the start of | |
1462 | each server generation from InitExtensions(), which is called from | |
1463 | the X server's main() function after all output devices have been | |
1464 | initialized, but before any input devices have been initialized. | |
1465 | </para> | |
1466 | ||
1467 | <para>PanoramiXNumScreens is set to the number of physical screens. If | |
1468 | only one physical screen is present, the extension is disabled, and | |
1469 | PanoramiXExtensionInit() returns without doing anything else. | |
1470 | </para> | |
1471 | ||
1472 | <para>The Xinerama extension is registered by calling AddExtension(). | |
1473 | </para> | |
1474 | ||
1475 | <para>GC and Screen private | |
1476 | indexes are allocated, and both GC and Screen private areas are | |
1477 | allocated for each physical screen. These hold Xinerama-specific | |
1478 | per-GC and per-Screen data. Each screen's CreateGC and CloseScreen | |
1479 | functions are wrapped by XineramaCreateGC() and | |
1480 | XineramaCloseScreen() respectively. Some new resource classes are | |
1481 | created for Xinerama drawables and GCs, and resource types for | |
1482 | Xinerama windows, pixmaps and colormaps. | |
1483 | </para> | |
1484 | ||
1485 | <para>A region (PanoramiXScreenRegion) is | |
1486 | initialized to be the union of the screen regions. | |
1487 | The relative positioning information for the | |
1488 | physical screens is taken from the ScreenRec x and y members, which | |
1489 | the DDX layer must initialize in InitOutput(). The bounds of the | |
1490 | combined screen is also calculated (PanoramiXPixWidth and | |
1491 | PanoramiXPixHeight). | |
1492 | </para> | |
1493 | ||
1494 | <para>The DIX layer has a list of function pointers | |
1495 | (ProcVector[]) that | |
1496 | holds the entry points for the functions that process core protocol | |
1497 | requests. The requests that Xinerama must intercept and break up | |
1498 | into physical screen-specific requests are wrapped. The original | |
1499 | set is copied to SavedProcVector[]. The types of requests | |
1500 | intercepted are Window requests, GC requests, colormap requests, | |
1501 | drawing requests, and some geometry-related requests. This wrapping | |
1502 | allows the bulk of the protocol request processing to be handled | |
1503 | transparently to the DIX layer. Some operations cannot be dealt with | |
1504 | in this way and are handled with Xinerama-specific code within the | |
1505 | DIX layer. | |
1506 | </para> | |
1507 | </listitem></varlistentry> | |
1508 | ||
1509 | <varlistentry> | |
1510 | <term>PanoramiXConsolidate()</term> | |
1511 | <listitem> | |
1512 | <para>PanoramiXConsolidate() is a | |
1513 | device-independent extension function that is called directly from | |
1514 | the X server's main() function after extensions and input/output | |
1515 | devices have been initialized, and before the root windows are | |
1516 | defined and initialized. | |
1517 | </para> | |
1518 | ||
1519 | <para>This function finds the set of depths (PanoramiXDepths[]) and | |
1520 | visuals (PanoramiXVisuals[]) | |
1521 | common to all of the physical screens. | |
1522 | PanoramiXNumDepths is set to the number of common depths, and | |
1523 | PanoramiXNumVisuals is set to the number of common visuals. | |
1524 | Resources are created for the single root window and the default | |
1525 | colormap. Each of these resources has per-physical screen entries. | |
1526 | </para> | |
1527 | </listitem></varlistentry> | |
1528 | ||
1529 | <varlistentry> | |
1530 | <term>PanoramiXCreateConnectionBlock()</term> | |
1531 | <listitem> | |
1532 | <para>PanoramiXConsolidate() is a | |
1533 | device-independent extension function that is called directly from | |
1534 | the X server's main() function after the per-physical screen root | |
1535 | windows are created. It is called instead of the standard DIX | |
1536 | CreateConnectionBlock() function. If this function returns FALSE, | |
1537 | the X server exits with a fatal error. This function will return | |
1538 | FALSE if no common depths were found in PanoramiXConsolidate(). | |
1539 | With no common depths, Xinerama mode is not possible. | |
1540 | </para> | |
1541 | ||
1542 | <para>The connection block holds the information that clients get when | |
1543 | they open a connection to the X server. It includes information | |
1544 | such as the supported pixmap formats, number of screens and the | |
1545 | sizes, depths, visuals, default colormap information, etc, for each | |
1546 | of the screens (much of information that <command>xdpyinfo</command> shows). The | |
1547 | connection block is initialized with the combined single screen | |
1548 | values that were calculated in the above two functions. | |
1549 | </para> | |
1550 | ||
1551 | <para>The Xinerama extension allows the registration of connection | |
1552 | block callback functions. The purpose of these is to allow other | |
1553 | extensions to do processing at this point. These callbacks can be | |
1554 | registered by calling XineramaRegisterConnectionBlockCallback() from | |
1555 | the other extension's ExtensionInit() function. Each registered | |
1556 | connection block callback is called at the end of | |
1557 | PanoramiXCreateConnectionBlock(). | |
1558 | </para> | |
1559 | </listitem></varlistentry> | |
1560 | </variablelist> | |
1561 | ||
1562 | <sect3> | |
1563 | <title>Xinerama-specific changes to the DIX code</title> | |
1564 | ||
1565 | <para>There are a few types of Xinerama-specific changes within the DIX | |
1566 | code. The main ones are described here. | |
1567 | </para> | |
1568 | ||
1569 | <para>Functions that deal with colormap or GC -related operations outside of | |
1570 | the intercepted protocol requests have a test added to only do the | |
1571 | processing for screen numbers > 0. This is because they are handled for | |
1572 | the single Xinerama screen and the processing is done once for screen 0. | |
1573 | </para> | |
1574 | ||
1575 | <para>The handling of motion events does some coordinate translation between | |
1576 | the physical screen's origin and screen zero's origin. Also, motion | |
1577 | events must be reported relative to the composite screen origin rather | |
1578 | than the physical screen origins. | |
1579 | </para> | |
1580 | ||
1581 | <para>There is some special handling for cursor, window and event processing | |
1582 | that cannot (either not at all or not conveniently) be done via the | |
1583 | intercepted protocol requests. A particular case is the handling of | |
1584 | pointers moving between physical screens. | |
1585 | </para> | |
1586 | </sect3> | |
1587 | ||
1588 | <sect3> | |
1589 | <title>Xinerama-specific changes to the MI code</title> | |
1590 | ||
1591 | <para>The only Xinerama-specific change to the MI code is in miSendExposures() | |
1592 | to handle the coordinate (and window ID) translation for expose events. | |
1593 | </para> | |
1594 | </sect3> | |
1595 | ||
1596 | <sect3> | |
1597 | <title>Intercepted DIX core requests</title> | |
1598 | ||
1599 | <para>Xinerama breaks up drawing requests for dispatch to each physical | |
1600 | screen. It also breaks up windows into pieces for each physical screen. | |
1601 | GCs are translated into per-screen GCs. Colormaps are replicated on | |
1602 | each physical screen. The functions handling the intercepted requests | |
1603 | take care of breaking the requests and repackaging them so that they can | |
1604 | be passed to the standard request handling functions for each screen in | |
1605 | turn. In addition, and to aid the repackaging, the information from | |
1606 | many of the intercepted requests is used to keep up to date the | |
1607 | necessary state information for the single composite screen. Requests | |
1608 | (usually those with replies) that can be satisfied completely from this | |
1609 | stored state information do not call the standard request handling | |
1610 | functions. | |
1611 | </para> | |
1612 | ||
1613 | </sect3> | |
1614 | ||
1615 | </sect2> | |
1616 | ||
1617 | </sect1> | |
1618 | ||
1619 | <!-- ============================================================ --> | |
1620 | ||
1621 | <sect1> | |
1622 | <title>Development Results</title> | |
1623 | ||
1624 | <para>In this section the results of each phase of development are | |
1625 | discussed. This development took place between approximately June 2001 | |
1626 | and July 2003. | |
1627 | </para> | |
1628 | ||
1629 | <sect2> | |
1630 | <title>Phase I</title> | |
1631 | ||
1632 | <para>The initial development phase dealt with the basic implementation | |
1633 | including the bootstrap code, which used the shadow framebuffer, and the | |
1634 | unoptimized implementation, based on an Xnest-style implementation. | |
1635 | </para> | |
1636 | ||
1637 | <sect3> | |
1638 | <title>Scope</title> | |
1639 | ||
1640 | <para>The goal of Phase I is to provide fundamental functionality that can | |
1641 | act as a foundation for ongoing work: | |
1642 | <orderedlist> | |
1643 | <listitem> | |
1644 | <para>Develop the proxy X server | |
1645 | <itemizedlist> | |
1646 | <listitem> | |
1647 | <para>The proxy X server will operate on the X11 protocol and | |
1648 | relay requests as necessary to correctly perform the request. | |
1649 | </para></listitem> | |
1650 | <listitem> | |
1651 | <para>Work will be based on the existing work for Xinerama and | |
1652 | Xnest. | |
1653 | </para></listitem> | |
1654 | <listitem> | |
1655 | <para>Input events and windowing operations are handled in the | |
1656 | proxy server and rendering requests are repackaged and sent to | |
1657 | each of the back-end servers for display. | |
1658 | </para></listitem> | |
1659 | <listitem> | |
1660 | <para>The multiple screen layout (including support for | |
1661 | overlapping screens) will be user configurable via a | |
1662 | configuration file or through the configuration tool. | |
1663 | </para></listitem> | |
1664 | </itemizedlist> | |
1665 | </para></listitem> | |
1666 | <listitem> | |
1667 | <para>Develop graphical configuration tool | |
1668 | <itemizedlist> | |
1669 | <listitem> | |
1670 | <para>There will be potentially a large number of X servers to | |
1671 | configure into a single display. The tool will allow the user | |
1672 | to specify which servers are involved in the configuration and | |
1673 | how they should be laid out. | |
1674 | </para></listitem> | |
1675 | </itemizedlist> | |
1676 | </para></listitem> | |
1677 | <listitem> | |
1678 | <para>Pass the X Test Suite | |
1679 | <itemizedlist> | |
1680 | <listitem> | |
1681 | <para>The X Test Suite covers the basic X11 operations. All | |
1682 | tests known to succeed must correctly operate in the distributed | |
1683 | X environment. | |
1684 | </para></listitem> | |
1685 | </itemizedlist> | |
1686 | </para></listitem> | |
1687 | </orderedlist> | |
1688 | ||
1689 | </para> | |
1690 | ||
1691 | <para>For this phase, the back-end X servers are assumed to be unmodified X | |
1692 | servers that do not support any DMX-related protocol extensions; future | |
1693 | optimization pathways are considered, but are not implemented; and the | |
1694 | configuration tool is assumed to rely only on libraries in the X source | |
1695 | tree (e.g., Xt). | |
1696 | </para> | |
1697 | </sect3> | |
1698 | ||
1699 | <sect3> | |
1700 | <title>Results</title> | |
1701 | ||
1702 | <para>The proxy X server, Xdmx, was developed to distribute X11 protocol | |
1703 | requests to the set of back-end X servers. It opens a window on each | |
1704 | back-end server, which represents the part of the front-end's root | |
1705 | window that is visible on that screen. It mirrors window, pixmap and | |
1706 | other state in each back-end server. Drawing requests are sent to | |
1707 | either windows or pixmaps on each back-end server. This code is based | |
1708 | on Xnest and uses the existing Xinerama extension. | |
1709 | </para> | |
1710 | ||
1711 | <para>Input events can be taken from (1) devices attached to the back-end | |
1712 | server, (2) core devices attached directly to the Xdmx server, or (3) | |
1713 | from a ``console'' window on another X server. Events for these devices | |
1714 | are gathered, processed and delivered to clients attached to the Xdmx | |
1715 | server. | |
1716 | </para> | |
1717 | ||
1718 | <para>An intuitive configuration format was developed to help the user | |
1719 | easily configure the multiple back-end X servers. It was defined (see | |
1720 | grammar in Xdmx man page) and a parser was implemented that is used by | |
1721 | the Xdmx server and by a standalone xdmxconfig utility. The parsing | |
1722 | support was implemented such that it can be easily factored out of the X | |
1723 | source tree for use with other tools (e.g., vdl). Support for | |
1724 | converting legacy vdl-format configuration files to the DMX format is | |
1725 | provided by the vdltodmx utility. | |
1726 | </para> | |
1727 | ||
1728 | <para>Originally, the configuration file was going to be a subsection of | |
1729 | XFree86's XF86Config file, but that was not possible since Xdmx is a | |
1730 | completely separate X server. Thus, a separate config file format was | |
1731 | developed. In addition, a graphical configuration | |
1732 | tool, xdmxconfig, was developed to allow the user to create and arrange | |
1733 | the screens in the configuration file. The <emphasis remap="bf">-configfile</emphasis> and <emphasis remap="bf">-config</emphasis> | |
1734 | command-line options can be used to start Xdmx using a configuration | |
1735 | file. | |
1736 | </para> | |
1737 | ||
1738 | <para>An extension that enables remote input testing is required for the X | |
1739 | Test Suite to function. During this phase, this extension (XTEST) was | |
1740 | implemented in the Xdmx server. The results from running the X Test | |
1741 | Suite are described in detail below. | |
1742 | </para> | |
1743 | </sect3> | |
1744 | ||
1745 | <sect3> | |
1746 | <title>X Test Suite</title> | |
1747 | ||
1748 | <sect4> | |
1749 | <title>Introduction</title> | |
1750 | <para> | |
1751 | The X Test Suite contains tests that verify Xlib functions | |
1752 | operate correctly. The test suite is designed to run on a | |
1753 | single X server; however, since X applications will not be | |
1754 | able to tell the difference between the DMX server and a | |
1755 | standard X server, the X Test Suite should also run on the | |
1756 | DMX server. | |
1757 | </para> | |
1758 | <para> | |
1759 | The Xdmx server was tested with the X Test Suite, and the | |
1760 | existing failures are noted in this section. To put these | |
1761 | results in perspective, we first discuss expected X Test | |
1762 | failures and how errors in underlying systems can impact | |
1763 | Xdmx test results. | |
1764 | </para> | |
1765 | </sect4> | |
1766 | ||
1767 | <sect4> | |
1768 | <title>Expected Failures for a Single Head</title> | |
1769 | <para> | |
1770 | A correctly implemented X server with a single screen is | |
1771 | expected to fail certain X Test tests. The following | |
1772 | well-known errors occur because of rounding error in the X | |
1773 | server code: | |
1774 | <literallayout> | |
1775 | XDrawArc: Tests 42, 63, 66, 73 | |
1776 | XDrawArcs: Tests 45, 66, 69, 76 | |
1777 | </literallayout> | |
1778 | </para> | |
1779 | <para> | |
1780 | The following failures occur because of the high-level X | |
1781 | server implementation: | |
1782 | <literallayout> | |
1783 | XLoadQueryFont: Test 1 | |
1784 | XListFontsWithInfo: Tests 3, 4 | |
1785 | XQueryFont: Tests 1, 2 | |
1786 | </literallayout> | |
1787 | </para> | |
1788 | <para> | |
1789 | The following test fails when running the X server as root | |
1790 | under Linux because of the way directory modes are | |
1791 | interpreted: | |
1792 | <literallayout> | |
1793 | XWriteBitmapFile: Test 3 | |
1794 | </literallayout> | |
1795 | </para> | |
1796 | <para> | |
1797 | Depending on the video card used for the back-end, other | |
1798 | failures may also occur because of bugs in the low-level | |
1799 | driver implementation. Over time, failures of this kind | |
1800 | are usually fixed by XFree86, but will show up in Xdmx | |
1801 | testing until then. | |
1802 | </para> | |
1803 | </sect4> | |
1804 | ||
1805 | <sect4> | |
1806 | <title>Expected Failures for Xinerama</title> | |
1807 | <para> | |
1808 | Xinerama fails several X Test Suite tests because of | |
1809 | design decisions made for the current implementation of | |
1810 | Xinerama. Over time, many of these errors will be | |
1811 | corrected by XFree86 and the group working on a new | |
1812 | Xinerama implementation. Therefore, Xdmx will also share | |
1813 | X Suite Test failures with Xinerama. | |
1814 | </para> | |
1815 | ||
1816 | <para> | |
1817 | We may be able to fix or work-around some of these | |
1818 | failures at the Xdmx level, but this will require | |
1819 | additional exploration that was not part of Phase I. | |
1820 | </para> | |
1821 | ||
1822 | <para> | |
1823 | Xinerama is constantly improving, and the list of | |
1824 | Xinerama-related failures depends on XFree86 version and | |
1825 | the underlying graphics hardware. We tested with a | |
1826 | variety of hardware, including nVidia, S3, ATI Radeon, | |
1827 | and Matrox G400 (in dual-head mode). The list below | |
1828 | includes only those failures that appear to be from the | |
1829 | Xinerama layer, and does not include failures listed in | |
1830 | the previous section, or failures that appear to be from | |
1831 | the low-level graphics driver itself: | |
1832 | </para> | |
1833 | ||
1834 | <para> | |
1835 | These failures were noted with multiple Xinerama | |
1836 | configurations: | |
1837 | <literallayout> | |
1838 | XCopyPlane: Tests 13, 22, 31 (well-known Xinerama implementation issue) | |
1839 | XSetFontPath: Test 4 | |
1840 | XGetDefault: Test 5 | |
1841 | XMatchVisualInfo: Test 1 | |
1842 | </literallayout> | |
1843 | </para> | |
1844 | <para> | |
1845 | These failures were noted only when using one dual-head | |
1846 | video card with a 4.2.99.x XFree86 server: | |
1847 | <literallayout> | |
1848 | XListPixmapFormats: Test 1 | |
1849 | XDrawRectangles: Test 45 | |
1850 | </literallayout> | |
1851 | </para> | |
1852 | <para> | |
1853 | These failures were noted only when using two video cards | |
1854 | from different vendors with a 4.1.99.x XFree86 server: | |
1855 | <literallayout> | |
1856 | XChangeWindowAttributes: Test 32 | |
1857 | XCreateWindow: Test 30 | |
1858 | XDrawLine: Test 22 | |
1859 | XFillArc: Test 22 | |
1860 | XChangeKeyboardControl: Tests 9, 10 | |
1861 | XRebindKeysym: Test 1 | |
1862 | </literallayout> | |
1863 | </para> | |
1864 | </sect4> | |
1865 | ||
1866 | <sect4> | |
1867 | <title>Additional Failures from Xdmx</title> | |
1868 | ||
1869 | <para> | |
1870 | When running Xdmx, no unexpected failures were noted. | |
1871 | Since the Xdmx server is based on Xinerama, we expect to | |
1872 | have most of the Xinerama failures present in the Xdmx | |
1873 | server. Similarly, since the Xdmx server must rely on the | |
1874 | low-level device drivers on each back-end server, we also | |
1875 | expect that Xdmx will exhibit most of the back-end | |
1876 | failures. Here is a summary: | |
1877 | <literallayout> | |
1878 | XListPixmapFormats: Test 1 (configuration dependent) | |
1879 | XChangeWindowAttributes: Test 32 | |
1880 | XCreateWindow: Test 30 | |
1881 | XCopyPlane: Test 13, 22, 31 | |
1882 | XSetFontPath: Test 4 | |
1883 | XGetDefault: Test 5 (configuration dependent) | |
1884 | XMatchVisualInfo: Test 1 | |
1885 | XRebindKeysym: Test 1 (configuration dependent) | |
1886 | </literallayout> | |
1887 | </para> | |
1888 | <para> | |
1889 | Note that this list is shorter than the combined list for | |
1890 | Xinerama because Xdmx uses different code paths to perform | |
1891 | some Xinerama operations. Further, some Xinerama failures | |
1892 | have been fixed in the XFree86 4.2.99.x CVS repository. | |
1893 | </para> | |
1894 | </sect4> | |
1895 | ||
1896 | <sect4> | |
1897 | <title>Summary and Future Work</title> | |
1898 | ||
1899 | <para> | |
1900 | Running the X Test Suite on Xdmx does not produce any | |
1901 | failures that cannot be accounted for by the underlying | |
1902 | Xinerama subsystem used by the front-end or by the | |
1903 | low-level device-driver code running on the back-end X | |
1904 | servers. The Xdmx server therefore is as ``correct'' as | |
1905 | possible with respect to the standard set of X Test Suite | |
1906 | tests. | |
1907 | </para> | |
1908 | ||
1909 | <para> | |
1910 | During the following phases, we will continue to verify | |
1911 | Xdmx correctness using the X Test Suite. We may also use | |
1912 | other tests suites or write additional tests that run | |
1913 | under the X Test Suite that specifically verify the | |
1914 | expected behavior of DMX. | |
1915 | </para> | |
1916 | </sect4> | |
1917 | </sect3> | |
1918 | ||
1919 | <sect3> | |
1920 | <title>Fonts</title> | |
1921 | ||
1922 | <para>In Phase I, fonts are handled directly by both the front-end and the | |
1923 | back-end servers, which is required since we must treat each back-end | |
1924 | server during this phase as a ``black box''. What this requires is that | |
1925 | <emphasis remap="bf">the front- and back-end servers must share the exact same font | |
1926 | path</emphasis>. There are two ways to help make sure that all servers share the | |
1927 | same font path: | |
1928 | ||
1929 | <orderedlist> | |
1930 | <listitem> | |
1931 | <para>First, each server can be configured to use the same font | |
1932 | server. The font server, xfs, can be configured to serve fonts to | |
1933 | multiple X servers via TCP. | |
1934 | </para></listitem> | |
1935 | ||
1936 | <listitem> | |
1937 | <para>Second, each server can be configured to use the same font | |
1938 | path and either those font paths can be copied to each back-end | |
1939 | machine or they can be mounted (e.g., via NFS) on each back-end | |
1940 | machine. | |
1941 | </para></listitem> | |
1942 | </orderedlist> | |
1943 | </para> | |
1944 | ||
1945 | <para>One additional concern is that a client program can set its own font | |
1946 | path, and if it does so, then that font path must be available on each | |
1947 | back-end machine. | |
1948 | </para> | |
1949 | ||
1950 | <para>The -fontpath command line option was added to allow users to | |
1951 | initialize the font path of the front end server. This font path is | |
1952 | propagated to each back-end server when the default font is loaded. If | |
1953 | there are any problems, an error message is printed, which will describe | |
1954 | the problem and list the current font path. For more information about | |
1955 | setting the font path, see the -fontpath option description in the man | |
1956 | page. | |
1957 | </para> | |
1958 | </sect3> | |
1959 | ||
1960 | <sect3> | |
1961 | <title>Performance</title> | |
1962 | ||
1963 | <para>Phase I of development was not intended to optimize performance. Its | |
1964 | focus was on completely and correctly handling the base X11 protocol in | |
1965 | the Xdmx server. However, several insights were gained during Phase I, | |
1966 | which are listed here for reference during the next phase of | |
1967 | development. | |
1968 | </para> | |
1969 | ||
1970 | <orderedlist> | |
1971 | <listitem> | |
1972 | <para>Calls to XSync() can slow down rendering since it requires a | |
1973 | complete round trip to and from a back-end server. This is | |
1974 | especially problematic when communicating over long haul networks. | |
1975 | </para></listitem> | |
1976 | ||
1977 | <listitem> | |
1978 | <para>Sending drawing requests to only the screens that they overlap | |
1979 | should improve performance. | |
1980 | </para></listitem> | |
1981 | </orderedlist> | |
1982 | </sect3> | |
1983 | ||
1984 | <sect3> | |
1985 | <title>Pixmaps</title> | |
1986 | ||
1987 | <para>Pixmaps were originally expected to be handled entirely in the | |
1988 | front-end X server; however, it was found that this overly complicated | |
1989 | the rendering code and would have required sending potentially large | |
1990 | images to each back server that required them when copying from pixmap | |
1991 | to screen. Thus, pixmap state is mirrored in the back-end server just | |
1992 | as it is with regular window state. With this implementation, the same | |
1993 | rendering code that draws to windows can be used to draw to pixmaps on | |
1994 | the back-end server, and no large image transfers are required to copy | |
1995 | from pixmap to window. | |
1996 | </para> | |
1997 | ||
1998 | </sect3> | |
1999 | ||
2000 | </sect2> | |
2001 | ||
2002 | <!-- ============================================================ --> | |
2003 | <sect2> | |
2004 | <title>Phase II</title> | |
2005 | ||
2006 | <para>The second phase of development concentrates on performance | |
2007 | optimizations. These optimizations are documented here, with | |
2008 | <command>x11perf</command> data to show how the optimizations improve performance. | |
2009 | </para> | |
2010 | ||
2011 | <para>All benchmarks were performed by running Xdmx on a dual processor | |
2012 | 1.4GHz AMD Athlon machine with 1GB of RAM connecting over 100baseT to | |
2013 | two single-processor 1GHz Pentium III machines with 256MB of RAM and ATI | |
2014 | Rage 128 (RF) video cards. The front end was running Linux | |
2015 | 2.4.20-pre1-ac1 and the back ends were running Linux 2.4.7-10 and | |
2016 | version 4.2.99.1 of XFree86 pulled from the XFree86 CVS repository on | |
2017 | August 7, 2002. All systems were running Red Hat Linux 7.2. | |
2018 | </para> | |
2019 | ||
2020 | <sect3> | |
2021 | <title>Moving from XFree86 4.1.99.1 to 4.2.0.0</title> | |
2022 | ||
2023 | <para>For phase II, the working source tree was moved to the branch tagged | |
2024 | with dmx-1-0-branch and was updated from version 4.1.99.1 (20 August | |
2025 | 2001) of the XFree86 sources to version 4.2.0.0 (18 January 2002). | |
2026 | After this update, the following tests were noted to be more than 10% | |
2027 | faster: | |
2028 | <screen> | |
2029 | 1.13 Fill 300x300 opaque stippled trapezoid (161x145 stipple) | |
2030 | 1.16 Fill 1x1 tiled trapezoid (161x145 tile) | |
2031 | 1.13 Fill 10x10 tiled trapezoid (161x145 tile) | |
2032 | 1.17 Fill 100x100 tiled trapezoid (161x145 tile) | |
2033 | 1.16 Fill 1x1 tiled trapezoid (216x208 tile) | |
2034 | 1.20 Fill 10x10 tiled trapezoid (216x208 tile) | |
2035 | 1.15 Fill 100x100 tiled trapezoid (216x208 tile) | |
2036 | 1.37 Circulate Unmapped window (200 kids) | |
2037 | </screen> | |
2038 | And the following tests were noted to be more than 10% slower: | |
2039 | <screen> | |
2040 | 0.88 Unmap window via parent (25 kids) | |
2041 | 0.75 Circulate Unmapped window (4 kids) | |
2042 | 0.79 Circulate Unmapped window (16 kids) | |
2043 | 0.80 Circulate Unmapped window (25 kids) | |
2044 | 0.82 Circulate Unmapped window (50 kids) | |
2045 | 0.85 Circulate Unmapped window (75 kids) | |
2046 | </screen> | |
2047 | </para> | |
2048 | ||
2049 | <para>These changes were not caused by any changes in the DMX system, and | |
2050 | may point to changes in the XFree86 tree or to tests that have more | |
2051 | "jitter" than most other <command>x11perf</command> tests. | |
2052 | </para> | |
2053 | </sect3> | |
2054 | ||
2055 | <sect3> | |
2056 | <title>Global changes</title> | |
2057 | ||
2058 | <para>During the development of the Phase II DMX server, several global | |
2059 | changes were made. These changes were also compared with the Phase I | |
2060 | server. The following tests were noted to be more than 10% faster: | |
2061 | <screen> | |
2062 | 1.13 Fill 300x300 opaque stippled trapezoid (161x145 stipple) | |
2063 | 1.15 Fill 1x1 tiled trapezoid (161x145 tile) | |
2064 | 1.13 Fill 10x10 tiled trapezoid (161x145 tile) | |
2065 | 1.17 Fill 100x100 tiled trapezoid (161x145 tile) | |
2066 | 1.16 Fill 1x1 tiled trapezoid (216x208 tile) | |
2067 | 1.19 Fill 10x10 tiled trapezoid (216x208 tile) | |
2068 | 1.15 Fill 100x100 tiled trapezoid (216x208 tile) | |
2069 | 1.15 Circulate Unmapped window (4 kids) | |
2070 | </screen> | |
2071 | </para> | |
2072 | ||
2073 | <para>The following tests were noted to be more than 10% slower: | |
2074 | <screen> | |
2075 | 0.69 Scroll 10x10 pixels | |
2076 | 0.68 Scroll 100x100 pixels | |
2077 | 0.68 Copy 10x10 from window to window | |
2078 | 0.68 Copy 100x100 from window to window | |
2079 | 0.76 Circulate Unmapped window (75 kids) | |
2080 | 0.83 Circulate Unmapped window (100 kids) | |
2081 | </screen> | |
2082 | </para> | |
2083 | ||
2084 | <para>For the remainder of this analysis, the baseline of comparison will | |
2085 | be the Phase II deliverable with all optimizations disabled (unless | |
2086 | otherwise noted). This will highlight how the optimizations in | |
2087 | isolation impact performance. | |
2088 | </para> | |
2089 | </sect3> | |
2090 | ||
2091 | <sect3> | |
2092 | <title>XSync() Batching</title> | |
2093 | ||
2094 | <para>During the Phase I implementation, XSync() was called after every | |
2095 | protocol request made by the DMX server. This provided the DMX server | |
2096 | with an interactive feel, but defeated X11's protocol buffering system | |
2097 | and introduced round-trip wire latency into every operation. During | |
2098 | Phase II, DMX was changed so that protocol requests are no longer | |
2099 | followed by calls to XSync(). Instead, the need for an XSync() is | |
2100 | noted, and XSync() calls are only made every 100mS or when the DMX | |
2101 | server specifically needs to make a call to guarantee interactivity. | |
2102 | With this new system, X11 buffers protocol as much as possible during a | |
2103 | 100mS interval, and many unnecessary XSync() calls are avoided. | |
2104 | </para> | |
2105 | ||
2106 | <para>Out of more than 300 <command>x11perf</command> tests, 8 tests became more than 100 | |
2107 | times faster, with 68 more than 50X faster, 114 more than 10X faster, | |
2108 | and 181 more than 2X faster. See table below for summary. | |
2109 | </para> | |
2110 | ||
2111 | <para>The following tests were noted to be more than 10% slower with | |
2112 | XSync() batching on: | |
2113 | <screen> | |
2114 | 0.88 500x500 tiled rectangle (161x145 tile) | |
2115 | 0.89 Copy 500x500 from window to window | |
2116 | </screen> | |
2117 | </para> | |
2118 | </sect3> | |
2119 | ||
2120 | <sect3> | |
2121 | <title>Offscreen Optimization</title> | |
2122 | ||
2123 | <para>Windows span one or more of the back-end servers' screens; however, | |
2124 | during Phase I development, windows were created on every back-end | |
2125 | server and every rendering request was sent to every window regardless | |
2126 | of whether or not that window was visible. With the offscreen | |
2127 | optimization, the DMX server tracks when a window is completely off of a | |
2128 | back-end server's screen and, in that case, it does not send rendering | |
2129 | requests to those back-end windows. This optimization saves bandwidth | |
2130 | between the front and back-end servers, and it reduces the number of | |
2131 | XSync() calls. The performance tests were run on a DMX system with only | |
2132 | two back-end servers. Greater performance gains will be had as the | |
2133 | number of back-end servers increases. | |
2134 | </para> | |
2135 | ||
2136 | <para>Out of more than 300 <command>x11perf</command> tests, 3 tests were at least twice as | |
2137 | fast, and 146 tests were at least 10% faster. Two tests were more than | |
2138 | 10% slower with the offscreen optimization: | |
2139 | <screen> | |
2140 | 0.88 Hide/expose window via popup (4 kids) | |
2141 | 0.89 Resize unmapped window (75 kids) | |
2142 | </screen> | |
2143 | </para> | |
2144 | </sect3> | |
2145 | ||
2146 | <sect3> | |
2147 | <title>Lazy Window Creation Optimization</title> | |
2148 | ||
2149 | <para>As mentioned above, during Phase I, windows were created on every | |
2150 | back-end server even if they were not visible on that back-end. With | |
2151 | the lazy window creation optimization, the DMX server does not create | |
2152 | windows on a back-end server until they are either visible or they | |
2153 | become the parents of a visible window. This optimization builds on the | |
2154 | offscreen optimization (described above) and requires it to be enabled. | |
2155 | </para> | |
2156 | ||
2157 | <para>The lazy window creation optimization works by creating the window | |
2158 | data structures in the front-end server when a client creates a window, | |
2159 | but delays creation of the window on the back-end server(s). A private | |
2160 | window structure in the DMX server saves the relevant window data and | |
2161 | tracks changes to the window's attributes and stacking order for later | |
2162 | use. The only times a window is created on a back-end server are (1) | |
2163 | when it is mapped and is at least partially overlapping the back-end | |
2164 | server's screen (tracked by the offscreen optimization), or (2) when the | |
2165 | window becomes the parent of a previously visible window. The first | |
2166 | case occurs when a window is mapped or when a visible window is copied, | |
2167 | moved or resized and now overlaps the back-end server's screen. The | |
2168 | second case occurs when starting a window manager after having created | |
2169 | windows to which the window manager needs to add decorations. | |
2170 | </para> | |
2171 | ||
2172 | <para>When either case occurs, a window on the back-end server is created | |
2173 | using the data saved in the DMX server's window private data structure. | |
2174 | The stacking order is then adjusted to correctly place the window on the | |
2175 | back-end and lastly the window is mapped. From this time forward, the | |
2176 | window is handled exactly as if the window had been created at the time | |
2177 | of the client's request. | |
2178 | </para> | |
2179 | ||
2180 | <para>Note that when a window is no longer visible on a back-end server's | |
2181 | screen (e.g., it is moved offscreen), the window is not destroyed; | |
2182 | rather, it is kept and reused later if the window once again becomes | |
2183 | visible on the back-end server's screen. Originally with this | |
2184 | optimization, destroying windows was implemented but was later rejected | |
2185 | because it increased bandwidth when windows were opaquely moved or | |
2186 | resized, which is common in many window managers. | |
2187 | </para> | |
2188 | ||
2189 | <para>The performance tests were run on a DMX system with only two back-end | |
2190 | servers. Greater performance gains will be had as the number of | |
2191 | back-end servers increases. | |
2192 | </para> | |
2193 | ||
2194 | <para>This optimization improved the following <command>x11perf</command> tests by more | |
2195 | than 10%: | |
2196 | <screen> | |
2197 | 1.10 500x500 rectangle outline | |
2198 | 1.12 Fill 100x100 stippled trapezoid (161x145 stipple) | |
2199 | 1.20 Circulate Unmapped window (50 kids) | |
2200 | 1.19 Circulate Unmapped window (75 kids) | |
2201 | </screen> | |
2202 | </para> | |
2203 | </sect3> | |
2204 | ||
2205 | <sect3> | |
2206 | <title>Subdividing Rendering Primitives</title> | |
2207 | ||
2208 | <para>X11 imaging requests transfer significant data between the client and | |
2209 | the X server. During Phase I, the DMX server would then transfer the | |
2210 | image data to each back-end server. Even with the offscreen | |
2211 | optimization (above), these requests still required transferring | |
2212 | significant data to each back-end server that contained a visible | |
2213 | portion of the window. For example, if the client uses XPutImage() to | |
2214 | copy an image to a window that overlaps the entire DMX screen, then the | |
2215 | entire image is copied by the DMX server to every back-end server. | |
2216 | </para> | |
2217 | ||
2218 | <para>To reduce the amount of data transferred between the DMX server and | |
2219 | the back-end servers when XPutImage() is called, the image data is | |
2220 | subdivided and only the data that will be visible on a back-end server's | |
2221 | screen is sent to that back-end server. Xinerama already implements a | |
2222 | subdivision algorithm for XGetImage() and no further optimization was | |
2223 | needed. | |
2224 | </para> | |
2225 | ||
2226 | <para>Other rendering primitives were analyzed, but the time required to | |
2227 | subdivide these primitives was a significant proportion of the time | |
2228 | required to send the entire rendering request to the back-end server, so | |
2229 | this optimization was rejected for the other rendering primitives. | |
2230 | </para> | |
2231 | ||
2232 | <para>Again, the performance tests were run on a DMX system with only two | |
2233 | back-end servers. Greater performance gains will be had as the number | |
2234 | of back-end servers increases. | |
2235 | </para> | |
2236 | ||
2237 | <para>This optimization improved the following <command>x11perf</command> tests by more | |
2238 | than 10%: | |
2239 | <screen> | |
2240 | 1.12 Fill 100x100 stippled trapezoid (161x145 stipple) | |
2241 | 1.26 PutImage 10x10 square | |
2242 | 1.83 PutImage 100x100 square | |
2243 | 1.91 PutImage 500x500 square | |
2244 | 1.40 PutImage XY 10x10 square | |
2245 | 1.48 PutImage XY 100x100 square | |
2246 | 1.50 PutImage XY 500x500 square | |
2247 | 1.45 Circulate Unmapped window (75 kids) | |
2248 | 1.74 Circulate Unmapped window (100 kids) | |
2249 | </screen> | |
2250 | </para> | |
2251 | ||
2252 | <para>The following test was noted to be more than 10% slower with this | |
2253 | optimization: | |
2254 | <screen> | |
2255 | 0.88 10-pixel fill chord partial circle | |
2256 | </screen> | |
2257 | </para> | |
2258 | </sect3> | |
2259 | ||
2260 | <sect3> | |
2261 | <title>Summary of x11perf Data</title> | |
2262 | ||
2263 | <para>With all of the optimizations on, 53 <command>x11perf</command> tests are more than | |
2264 | 100X faster than the unoptimized Phase II deliverable, with 69 more than | |
2265 | 50X faster, 73 more than 10X faster, and 199 more than twice as fast. | |
2266 | No tests were more than 10% slower than the unoptimized Phase II | |
2267 | deliverable. (Compared with the Phase I deliverable, only Circulate | |
2268 | Unmapped window (100 kids) was more than 10% slower than the Phase II | |
2269 | deliverable. As noted above, this test seems to have wider variability | |
2270 | than other <command>x11perf</command> tests.) | |
2271 | </para> | |
2272 | ||
2273 | <para>The following table summarizes relative <command>x11perf</command> test changes for | |
2274 | all optimizations individually and collectively. Note that some of the | |
2275 | optimizations have a synergistic effect when used together. | |
2276 | <screen> | |
2277 | ||
2278 | 1: XSync() batching only | |
2279 | 2: Off screen optimizations only | |
2280 | 3: Window optimizations only | |
2281 | 4: Subdivprims only | |
2282 | 5: All optimizations | |
2283 | ||
2284 | 1 2 3 4 5 Operation | |
2285 | ------ ---- ---- ---- ------ --------- | |
2286 | 2.14 1.85 1.00 1.00 4.13 Dot | |
2287 | 1.67 1.80 1.00 1.00 3.31 1x1 rectangle | |
2288 | 2.38 1.43 1.00 1.00 2.44 10x10 rectangle | |
2289 | 1.00 1.00 0.92 0.98 1.00 100x100 rectangle | |
2290 | 1.00 1.00 1.00 1.00 1.00 500x500 rectangle | |
2291 | 1.83 1.85 1.05 1.06 3.54 1x1 stippled rectangle (8x8 stipple) | |
2292 | 2.43 1.43 1.00 1.00 2.41 10x10 stippled rectangle (8x8 stipple) | |
2293 | 0.98 1.00 1.00 1.00 1.00 100x100 stippled rectangle (8x8 stipple) | |
2294 | 1.00 1.00 1.00 1.00 0.98 500x500 stippled rectangle (8x8 stipple) | |
2295 | 1.75 1.75 1.00 1.00 3.40 1x1 opaque stippled rectangle (8x8 stipple) | |
2296 | 2.38 1.42 1.00 1.00 2.34 10x10 opaque stippled rectangle (8x8 stipple) | |
2297 | 1.00 1.00 0.97 0.97 1.00 100x100 opaque stippled rectangle (8x8 stipple) | |
2298 | 1.00 1.00 1.00 1.00 0.99 500x500 opaque stippled rectangle (8x8 stipple) | |
2299 | 1.82 1.82 1.04 1.04 3.56 1x1 tiled rectangle (4x4 tile) | |
2300 | 2.33 1.42 1.00 1.00 2.37 10x10 tiled rectangle (4x4 tile) | |
2301 | 1.00 0.92 1.00 1.00 1.00 100x100 tiled rectangle (4x4 tile) | |
2302 | 1.00 1.00 1.00 1.00 1.00 500x500 tiled rectangle (4x4 tile) | |
2303 | 1.94 1.62 1.00 1.00 3.66 1x1 stippled rectangle (17x15 stipple) | |
2304 | 1.74 1.28 1.00 1.00 1.73 10x10 stippled rectangle (17x15 stipple) | |
2305 | 1.00 1.00 1.00 0.89 0.98 100x100 stippled rectangle (17x15 stipple) | |
2306 | 1.00 1.00 1.00 1.00 0.98 500x500 stippled rectangle (17x15 stipple) | |
2307 | 1.94 1.62 1.00 1.00 3.67 1x1 opaque stippled rectangle (17x15 stipple) | |
2308 | 1.69 1.26 1.00 1.00 1.66 10x10 opaque stippled rectangle (17x15 stipple) | |
2309 | 1.00 0.95 1.00 1.00 1.00 100x100 opaque stippled rectangle (17x15 stipple) | |
2310 | 1.00 1.00 1.00 1.00 0.97 500x500 opaque stippled rectangle (17x15 stipple) | |
2311 | 1.93 1.61 0.99 0.99 3.69 1x1 tiled rectangle (17x15 tile) | |
2312 | 1.73 1.27 1.00 1.00 1.72 10x10 tiled rectangle (17x15 tile) | |
2313 | 1.00 1.00 1.00 1.00 0.98 100x100 tiled rectangle (17x15 tile) | |
2314 | 1.00 1.00 0.97 0.97 1.00 500x500 tiled rectangle (17x15 tile) | |
2315 | 1.95 1.63 1.00 1.00 3.83 1x1 stippled rectangle (161x145 stipple) | |
2316 | 1.80 1.30 1.00 1.00 1.83 10x10 stippled rectangle (161x145 stipple) | |
2317 | 0.97 1.00 1.00 1.00 1.01 100x100 stippled rectangle (161x145 stipple) | |
2318 | 1.00 1.00 1.00 1.00 0.98 500x500 stippled rectangle (161x145 stipple) | |
2319 | 1.95 1.63 1.00 1.00 3.56 1x1 opaque stippled rectangle (161x145 stipple) | |
2320 | 1.65 1.25 1.00 1.00 1.68 10x10 opaque stippled rectangle (161x145 stipple) | |
2321 | 1.00 1.00 1.00 1.00 1.01 100x100 opaque stippled rectangle (161x145... | |
2322 | 1.00 1.00 1.00 1.00 0.97 500x500 opaque stippled rectangle (161x145... | |
2323 | 1.95 1.63 0.98 0.99 3.80 1x1 tiled rectangle (161x145 tile) | |
2324 | 1.67 1.26 1.00 1.00 1.67 10x10 tiled rectangle (161x145 tile) | |
2325 | 1.13 1.14 1.14 1.14 1.14 100x100 tiled rectangle (161x145 tile) | |
2326 | 0.88 1.00 1.00 1.00 0.99 500x500 tiled rectangle (161x145 tile) | |
2327 | 1.93 1.63 1.00 1.00 3.53 1x1 tiled rectangle (216x208 tile) | |
2328 | 1.69 1.26 1.00 1.00 1.66 10x10 tiled rectangle (216x208 tile) | |
2329 | 1.00 1.00 1.00 1.00 1.00 100x100 tiled rectangle (216x208 tile) | |
2330 | 1.00 1.00 1.00 1.00 1.00 500x500 tiled rectangle (216x208 tile) | |
2331 | 1.82 1.70 1.00 1.00 3.38 1-pixel line segment | |
2332 | 2.07 1.56 0.90 1.00 3.31 10-pixel line segment | |
2333 | 1.29 1.10 1.00 1.00 1.27 100-pixel line segment | |
2334 | 1.05 1.06 1.03 1.03 1.09 500-pixel line segment | |
2335 | 1.30 1.13 1.00 1.00 1.29 100-pixel line segment (1 kid) | |
2336 | 1.32 1.15 1.00 1.00 1.32 100-pixel line segment (2 kids) | |
2337 | 1.33 1.16 1.00 1.00 1.33 100-pixel line segment (3 kids) | |
2338 | 1.92 1.64 1.00 1.00 3.73 10-pixel dashed segment | |
2339 | 1.34 1.16 1.00 1.00 1.34 100-pixel dashed segment | |
2340 | 1.24 1.11 0.99 0.97 1.23 100-pixel double-dashed segment | |
2341 | 1.72 1.77 1.00 1.00 3.25 10-pixel horizontal line segment | |
2342 | 1.83 1.66 1.01 1.00 3.54 100-pixel horizontal line segment | |
2343 | 1.86 1.30 1.00 1.00 1.84 500-pixel horizontal line segment | |
2344 | 2.11 1.52 1.00 0.99 3.02 10-pixel vertical line segment | |
2345 | 1.21 1.10 1.00 1.00 1.20 100-pixel vertical line segment | |
2346 | 1.03 1.03 1.00 1.00 1.02 500-pixel vertical line segment | |
2347 | 4.42 1.68 1.00 1.01 4.64 10x1 wide horizontal line segment | |
2348 | 1.83 1.31 1.00 1.00 1.83 100x10 wide horizontal line segment | |
2349 | 1.07 1.00 0.96 1.00 1.07 500x50 wide horizontal line segment | |
2350 | 4.10 1.67 1.00 1.00 4.62 10x1 wide vertical line segment | |
2351 | 1.50 1.24 1.06 1.06 1.48 100x10 wide vertical line segment | |
2352 | 1.06 1.03 1.00 1.00 1.05 500x50 wide vertical line segment | |
2353 | 2.54 1.61 1.00 1.00 3.61 1-pixel line | |
2354 | 2.71 1.48 1.00 1.00 2.67 10-pixel line | |
2355 | 1.19 1.09 1.00 1.00 1.19 100-pixel line | |
2356 | 1.04 1.02 1.00 1.00 1.03 500-pixel line | |
2357 | 2.68 1.51 0.98 1.00 3.17 10-pixel dashed line | |
2358 | 1.23 1.11 0.99 0.99 1.23 100-pixel dashed line | |
2359 | 1.15 1.08 1.00 1.00 1.15 100-pixel double-dashed line | |
2360 | 2.27 1.39 1.00 1.00 2.23 10x1 wide line | |
2361 | 1.20 1.09 1.00 1.00 1.20 100x10 wide line | |
2362 | 1.04 1.02 1.00 1.00 1.04 500x50 wide line | |
2363 | 1.52 1.45 1.00 1.00 1.52 100x10 wide dashed line | |
2364 | 1.54 1.47 1.00 1.00 1.54 100x10 wide double-dashed line | |
2365 | 1.97 1.30 0.96 0.95 1.95 10x10 rectangle outline | |
2366 | 1.44 1.27 1.00 1.00 1.43 100x100 rectangle outline | |
2367 | 3.22 2.16 1.10 1.09 3.61 500x500 rectangle outline | |
2368 | 1.95 1.34 1.00 1.00 1.90 10x10 wide rectangle outline | |
2369 | 1.14 1.14 1.00 1.00 1.13 100x100 wide rectangle outline | |
2370 | 1.00 1.00 1.00 1.00 1.00 500x500 wide rectangle outline | |
2371 | 1.57 1.72 1.00 1.00 3.03 1-pixel circle | |
2372 | 1.96 1.35 1.00 1.00 1.92 10-pixel circle | |
2373 | 1.21 1.07 0.86 0.97 1.20 100-pixel circle | |
2374 | 1.08 1.04 1.00 1.00 1.08 500-pixel circle | |
2375 | 1.39 1.19 1.03 1.03 1.38 100-pixel dashed circle | |
2376 | 1.21 1.11 1.00 1.00 1.23 100-pixel double-dashed circle | |
2377 | 1.59 1.28 1.00 1.00 1.58 10-pixel wide circle | |
2378 | 1.22 1.12 0.99 1.00 1.22 100-pixel wide circle | |
2379 | 1.06 1.04 1.00 1.00 1.05 500-pixel wide circle | |
2380 | 1.87 1.84 1.00 1.00 1.85 100-pixel wide dashed circle | |
2381 | 1.90 1.93 1.01 1.01 1.90 100-pixel wide double-dashed circle | |
2382 | 2.13 1.43 1.00 1.00 2.32 10-pixel partial circle | |
2383 | 1.42 1.18 1.00 1.00 1.42 100-pixel partial circle | |
2384 | 1.92 1.85 1.01 1.01 1.89 10-pixel wide partial circle | |
2385 | 1.73 1.67 1.00 1.00 1.73 100-pixel wide partial circle | |
2386 | 1.36 1.95 1.00 1.00 2.64 1-pixel solid circle | |
2387 | 2.02 1.37 1.00 1.00 2.03 10-pixel solid circle | |
2388 | 1.19 1.09 1.00 1.00 1.19 100-pixel solid circle | |
2389 | 1.02 0.99 1.00 1.00 1.01 500-pixel solid circle | |
2390 | 1.74 1.28 1.00 0.88 1.73 10-pixel fill chord partial circle | |
2391 | 1.31 1.13 1.00 1.00 1.31 100-pixel fill chord partial circle | |
2392 | 1.67 1.31 1.03 1.03 1.72 10-pixel fill slice partial circle | |
2393 | 1.30 1.13 1.00 1.00 1.28 100-pixel fill slice partial circle | |
2394 | 2.45 1.49 1.01 1.00 2.71 10-pixel ellipse | |
2395 | 1.22 1.10 1.00 1.00 1.22 100-pixel ellipse | |
2396 | 1.09 1.04 1.00 1.00 1.09 500-pixel ellipse | |
2397 | 1.90 1.28 1.00 1.00 1.89 100-pixel dashed ellipse | |
2398 | 1.62 1.24 0.96 0.97 1.61 100-pixel double-dashed ellipse | |
2399 | 2.43 1.50 1.00 1.00 2.42 10-pixel wide ellipse | |
2400 | 1.61 1.28 1.03 1.03 1.60 100-pixel wide ellipse | |
2401 | 1.08 1.05 1.00 1.00 1.08 500-pixel wide ellipse | |
2402 | 1.93 1.88 1.00 1.00 1.88 100-pixel wide dashed ellipse | |
2403 | 1.94 1.89 1.01 1.00 1.94 100-pixel wide double-dashed ellipse | |
2404 | 2.31 1.48 1.00 1.00 2.67 10-pixel partial ellipse | |
2405 | 1.38 1.17 1.00 1.00 1.38 100-pixel partial ellipse | |
2406 | 2.00 1.85 0.98 0.97 1.98 10-pixel wide partial ellipse | |
2407 | 1.89 1.86 1.00 1.00 1.89 100-pixel wide partial ellipse | |
2408 | 3.49 1.60 1.00 1.00 3.65 10-pixel filled ellipse | |
2409 | 1.67 1.26 1.00 1.00 1.67 100-pixel filled ellipse | |
2410 | 1.06 1.04 1.00 1.00 1.06 500-pixel filled ellipse | |
2411 | 2.38 1.43 1.01 1.00 2.32 10-pixel fill chord partial ellipse | |
2412 | 2.06 1.30 1.00 1.00 2.05 100-pixel fill chord partial ellipse | |
2413 | 2.27 1.41 1.00 1.00 2.27 10-pixel fill slice partial ellipse | |
2414 | 1.98 1.33 1.00 0.97 1.97 100-pixel fill slice partial ellipse | |
2415 | 57.46 1.99 1.01 1.00 114.92 Fill 1x1 equivalent triangle | |
2416 | 56.94 1.98 1.01 1.00 73.89 Fill 10x10 equivalent triangle | |
2417 | 6.07 1.75 1.00 1.00 6.07 Fill 100x100 equivalent triangle | |
2418 | 51.12 1.98 1.00 1.00 102.81 Fill 1x1 trapezoid | |
2419 | 51.42 1.82 1.01 1.00 94.89 Fill 10x10 trapezoid | |
2420 | 6.47 1.80 1.00 1.00 6.44 Fill 100x100 trapezoid | |
2421 | 1.56 1.28 1.00 0.99 1.56 Fill 300x300 trapezoid | |
2422 | 51.27 1.97 0.96 0.97 102.54 Fill 1x1 stippled trapezoid (8x8 stipple) | |
2423 | 51.73 2.00 1.02 1.02 67.92 Fill 10x10 stippled trapezoid (8x8 stipple) | |
2424 | 5.36 1.72 1.00 1.00 5.36 Fill 100x100 stippled trapezoid (8x8 stipple) | |
2425 | 1.54 1.26 1.00 1.00 1.59 Fill 300x300 stippled trapezoid (8x8 stipple) | |
2426 | 51.41 1.94 1.01 1.00 102.82 Fill 1x1 opaque stippled trapezoid (8x8 stipple) | |
2427 | 50.71 1.95 0.99 1.00 65.44 Fill 10x10 opaque stippled trapezoid (8x8... | |
2428 | 5.33 1.73 1.00 1.00 5.36 Fill 100x100 opaque stippled trapezoid (8x8... | |
2429 | 1.58 1.25 1.00 1.00 1.58 Fill 300x300 opaque stippled trapezoid (8x8... | |
2430 | 51.56 1.96 0.99 0.90 103.68 Fill 1x1 tiled trapezoid (4x4 tile) | |
2431 | 51.59 1.99 1.01 1.01 62.25 Fill 10x10 tiled trapezoid (4x4 tile) | |
2432 | 5.38 1.72 1.00 1.00 5.38 Fill 100x100 tiled trapezoid (4x4 tile) | |
2433 | 1.54 1.25 1.00 0.99 1.58 Fill 300x300 tiled trapezoid (4x4 tile) | |
2434 | 51.70 1.98 1.01 1.01 103.98 Fill 1x1 stippled trapezoid (17x15 stipple) | |
2435 | 44.86 1.97 1.00 1.00 44.86 Fill 10x10 stippled trapezoid (17x15 stipple) | |
2436 | 2.74 1.56 1.00 1.00 2.73 Fill 100x100 stippled trapezoid (17x15 stipple) | |
2437 | 1.29 1.14 1.00 1.00 1.27 Fill 300x300 stippled trapezoid (17x15 stipple) | |
2438 | 51.41 1.96 0.96 0.95 103.39 Fill 1x1 opaque stippled trapezoid (17x15... | |
2439 | 45.14 1.96 1.01 1.00 45.14 Fill 10x10 opaque stippled trapezoid (17x15... | |
2440 | 2.68 1.56 1.00 1.00 2.68 Fill 100x100 opaque stippled trapezoid (17x15... | |
2441 | 1.26 1.10 1.00 1.00 1.28 Fill 300x300 opaque stippled trapezoid (17x15... | |
2442 | 51.13 1.97 1.00 0.99 103.39 Fill 1x1 tiled trapezoid (17x15 tile) | |
2443 | 47.58 1.96 1.00 1.00 47.86 Fill 10x10 tiled trapezoid (17x15 tile) | |
2444 | 2.74 1.56 1.00 1.00 2.74 Fill 100x100 tiled trapezoid (17x15 tile) | |
2445 | 1.29 1.14 1.00 1.00 1.28 Fill 300x300 tiled trapezoid (17x15 tile) | |
2446 | 51.13 1.97 0.99 0.97 103.39 Fill 1x1 stippled trapezoid (161x145 stipple) | |
2447 | 45.14 1.97 1.00 1.00 44.29 Fill 10x10 stippled trapezoid (161x145 stipple) | |
2448 | 3.02 1.77 1.12 1.12 3.38 Fill 100x100 stippled trapezoid (161x145 stipple) | |
2449 | 1.31 1.13 1.00 1.00 1.30 Fill 300x300 stippled trapezoid (161x145 stipple) | |
2450 | 51.27 1.97 1.00 1.00 103.10 Fill 1x1 opaque stippled trapezoid (161x145... | |
2451 | 45.01 1.97 1.00 1.00 45.01 Fill 10x10 opaque stippled trapezoid (161x145... | |
2452 | 2.67 1.56 1.00 1.00 2.69 Fill 100x100 opaque stippled trapezoid (161x145.. | |
2453 | 1.29 1.13 1.00 1.01 1.27 Fill 300x300 opaque stippled trapezoid (161x145.. | |
2454 | 51.41 1.96 1.00 0.99 103.39 Fill 1x1 tiled trapezoid (161x145 tile) | |
2455 | 45.01 1.96 0.98 1.00 45.01 Fill 10x10 tiled trapezoid (161x145 tile) | |
2456 | 2.62 1.36 1.00 1.00 2.69 Fill 100x100 tiled trapezoid (161x145 tile) | |
2457 | 1.27 1.13 1.00 1.00 1.22 Fill 300x300 tiled trapezoid (161x145 tile) | |
2458 | 51.13 1.98 1.00 1.00 103.39 Fill 1x1 tiled trapezoid (216x208 tile) | |
2459 | 45.14 1.97 1.01 0.99 45.14 Fill 10x10 tiled trapezoid (216x208 tile) | |
2460 | 2.62 1.55 1.00 1.00 2.71 Fill 100x100 tiled trapezoid (216x208 tile) | |
2461 | 1.28 1.13 1.00 1.00 1.20 Fill 300x300 tiled trapezoid (216x208 tile) | |
2462 | 50.71 1.95 1.00 1.00 54.70 Fill 10x10 equivalent complex polygon | |
2463 | 5.51 1.71 0.96 0.98 5.47 Fill 100x100 equivalent complex polygons | |
2464 | 8.39 1.97 1.00 1.00 16.75 Fill 10x10 64-gon (Convex) | |
2465 | 8.38 1.83 1.00 1.00 8.43 Fill 100x100 64-gon (Convex) | |
2466 | 8.50 1.96 1.00 1.00 16.64 Fill 10x10 64-gon (Complex) | |
2467 | 8.26 1.83 1.00 1.00 8.35 Fill 100x100 64-gon (Complex) | |
2468 | 14.09 1.87 1.00 1.00 14.05 Char in 80-char line (6x13) | |
2469 | 11.91 1.87 1.00 1.00 11.95 Char in 70-char line (8x13) | |
2470 | 11.16 1.85 1.01 1.00 11.10 Char in 60-char line (9x15) | |
2471 | 10.09 1.78 1.00 1.00 10.09 Char16 in 40-char line (k14) | |
2472 | 6.15 1.75 1.00 1.00 6.31 Char16 in 23-char line (k24) | |
2473 | 11.92 1.90 1.03 1.03 11.88 Char in 80-char line (TR 10) | |
2474 | 8.18 1.78 1.00 0.99 8.17 Char in 30-char line (TR 24) | |
2475 | 42.83 1.44 1.01 1.00 42.11 Char in 20/40/20 line (6x13, TR 10) | |
2476 | 27.45 1.43 1.01 1.01 27.45 Char16 in 7/14/7 line (k14, k24) | |
2477 | 12.13 1.85 1.00 1.00 12.05 Char in 80-char image line (6x13) | |
2478 | 10.00 1.84 1.00 1.00 10.00 Char in 70-char image line (8x13) | |
2479 | 9.18 1.83 1.00 1.00 9.12 Char in 60-char image line (9x15) | |
2480 | 9.66 1.82 0.98 0.95 9.66 Char16 in 40-char image line (k14) | |
2481 | 5.82 1.72 1.00 1.00 5.99 Char16 in 23-char image line (k24) | |
2482 | 8.70 1.80 1.00 1.00 8.65 Char in 80-char image line (TR 10) | |
2483 | 4.67 1.66 1.00 1.00 4.67 Char in 30-char image line (TR 24) | |
2484 | 84.43 1.47 1.00 1.00 124.18 Scroll 10x10 pixels | |
2485 | 3.73 1.50 1.00 0.98 3.73 Scroll 100x100 pixels | |
2486 | 1.00 1.00 1.00 1.00 1.00 Scroll 500x500 pixels | |
2487 | 84.43 1.51 1.00 1.00 134.02 Copy 10x10 from window to window | |
2488 | 3.62 1.51 0.98 0.98 3.62 Copy 100x100 from window to window | |
2489 | 0.89 1.00 1.00 1.00 1.00 Copy 500x500 from window to window | |
2490 | 57.06 1.99 1.00 1.00 88.64 Copy 10x10 from pixmap to window | |
2491 | 2.49 2.00 1.00 1.00 2.48 Copy 100x100 from pixmap to window | |
2492 | 1.00 0.91 1.00 1.00 0.98 Copy 500x500 from pixmap to window | |
2493 | 2.04 1.01 1.00 1.00 2.03 Copy 10x10 from window to pixmap | |
2494 | 1.05 1.00 1.00 1.00 1.05 Copy 100x100 from window to pixmap | |
2495 | 1.00 1.00 0.93 1.00 1.04 Copy 500x500 from window to pixmap | |
2496 | 58.52 1.03 1.03 1.02 57.95 Copy 10x10 from pixmap to pixmap | |
2497 | 2.40 1.00 1.00 1.00 2.45 Copy 100x100 from pixmap to pixmap | |
2498 | 1.00 1.00 1.00 1.00 1.00 Copy 500x500 from pixmap to pixmap | |
2499 | 51.57 1.92 1.00 1.00 85.75 Copy 10x10 1-bit deep plane | |
2500 | 6.37 1.75 1.01 1.01 6.37 Copy 100x100 1-bit deep plane | |
2501 | 1.26 1.11 1.00 1.00 1.24 Copy 500x500 1-bit deep plane | |
2502 | 4.23 1.63 0.98 0.97 4.38 Copy 10x10 n-bit deep plane | |
2503 | 1.04 1.02 1.00 1.00 1.04 Copy 100x100 n-bit deep plane | |
2504 | 1.00 1.00 1.00 1.00 1.00 Copy 500x500 n-bit deep plane | |
2505 | 6.45 1.98 1.00 1.26 12.80 PutImage 10x10 square | |
2506 | 1.10 1.87 1.00 1.83 2.11 PutImage 100x100 square | |
2507 | 1.02 1.93 1.00 1.91 1.91 PutImage 500x500 square | |
2508 | 4.17 1.78 1.00 1.40 7.18 PutImage XY 10x10 square | |
2509 | 1.27 1.49 0.97 1.48 2.10 PutImage XY 100x100 square | |
2510 | 1.00 1.50 1.00 1.50 1.52 PutImage XY 500x500 square | |
2511 | 1.07 1.01 1.00 1.00 1.06 GetImage 10x10 square | |
2512 | 1.01 1.00 1.00 1.00 1.01 GetImage 100x100 square | |
2513 | 1.00 1.00 1.00 1.00 1.00 GetImage 500x500 square | |
2514 | 1.56 1.00 0.99 0.97 1.56 GetImage XY 10x10 square | |
2515 | 1.02 1.00 1.00 1.00 1.02 GetImage XY 100x100 square | |
2516 | 1.00 1.00 1.00 1.00 1.00 GetImage XY 500x500 square | |
2517 | 1.00 1.00 1.01 0.98 0.95 X protocol NoOperation | |
2518 | 1.02 1.03 1.04 1.03 1.00 QueryPointer | |
2519 | 1.03 1.02 1.04 1.03 1.00 GetProperty | |
2520 | 100.41 1.51 1.00 1.00 198.76 Change graphics context | |
2521 | 45.81 1.00 0.99 0.97 57.10 Create and map subwindows (4 kids) | |
2522 | 78.45 1.01 1.02 1.02 63.07 Create and map subwindows (16 kids) | |
2523 | 73.91 1.01 1.00 1.00 56.37 Create and map subwindows (25 kids) | |
2524 | 73.22 1.00 1.00 1.00 49.07 Create and map subwindows (50 kids) | |
2525 | 72.36 1.01 0.99 1.00 32.14 Create and map subwindows (75 kids) | |
2526 | 70.34 1.00 1.00 1.00 30.12 Create and map subwindows (100 kids) | |
2527 | 55.00 1.00 1.00 0.99 23.75 Create and map subwindows (200 kids) | |
2528 | 55.30 1.01 1.00 1.00 141.03 Create unmapped window (4 kids) | |
2529 | 55.38 1.01 1.01 1.00 163.25 Create unmapped window (16 kids) | |
2530 | 54.75 0.96 1.00 0.99 166.95 Create unmapped window (25 kids) | |
2531 | 54.83 1.00 1.00 0.99 178.81 Create unmapped window (50 kids) | |
2532 | 55.38 1.01 1.01 1.00 181.20 Create unmapped window (75 kids) | |
2533 | 55.38 1.01 1.01 1.00 181.20 Create unmapped window (100 kids) | |
2534 | 54.87 1.01 1.01 1.00 182.05 Create unmapped window (200 kids) | |
2535 | 28.13 1.00 1.00 1.00 30.75 Map window via parent (4 kids) | |
2536 | 36.14 1.01 1.01 1.01 32.58 Map window via parent (16 kids) | |
2537 | 26.13 1.00 0.98 0.95 29.85 Map window via parent (25 kids) | |
2538 | 40.07 1.00 1.01 1.00 27.57 Map window via parent (50 kids) | |
2539 | 23.26 0.99 1.00 1.00 18.23 Map window via parent (75 kids) | |
2540 | 22.91 0.99 1.00 0.99 16.52 Map window via parent (100 kids) | |
2541 | 27.79 1.00 1.00 0.99 12.50 Map window via parent (200 kids) | |
2542 | 22.35 1.00 1.00 1.00 56.19 Unmap window via parent (4 kids) | |
2543 | 9.57 1.00 0.99 1.00 89.78 Unmap window via parent (16 kids) | |
2544 | 80.77 1.01 1.00 1.00 103.85 Unmap window via parent (25 kids) | |
2545 | 96.34 1.00 1.00 1.00 116.06 Unmap window via parent (50 kids) | |
2546 | 99.72 1.00 1.00 1.00 124.93 Unmap window via parent (75 kids) | |
2547 | 112.36 1.00 1.00 1.00 125.27 Unmap window via parent (100 kids) | |
2548 | 105.41 1.00 1.00 0.99 120.00 Unmap window via parent (200 kids) | |
2549 | 51.29 1.03 1.02 1.02 74.19 Destroy window via parent (4 kids) | |
2550 | 86.75 0.99 0.99 0.99 116.87 Destroy window via parent (16 kids) | |
2551 | 106.43 1.01 1.01 1.01 127.49 Destroy window via parent (25 kids) | |
2552 | 120.34 1.01 1.01 1.00 140.11 Destroy window via parent (50 kids) | |
2553 | 126.67 1.00 0.99 0.99 145.00 Destroy window via parent (75 kids) | |
2554 | 126.11 1.01 1.01 1.00 140.56 Destroy window via parent (100 kids) | |
2555 | 128.57 1.01 1.00 1.00 137.91 Destroy window via parent (200 kids) | |
2556 | 16.04 0.88 1.00 1.00 20.36 Hide/expose window via popup (4 kids) | |
2557 | 19.04 1.01 1.00 1.00 23.48 Hide/expose window via popup (16 kids) | |
2558 | 19.22 1.00 1.00 1.00 20.44 Hide/expose window via popup (25 kids) | |
2559 | 17.41 1.00 0.91 0.97 17.68 Hide/expose window via popup (50 kids) | |
2560 | 17.29 1.01 1.00 1.01 17.07 Hide/expose window via popup (75 kids) | |
2561 | 16.74 1.00 1.00 1.00 16.17 Hide/expose window via popup (100 kids) | |
2562 | 10.30 1.00 1.00 1.00 10.51 Hide/expose window via popup (200 kids) | |
2563 | 16.48 1.01 1.00 1.00 26.05 Move window (4 kids) | |
2564 | 17.01 0.95 1.00 1.00 23.97 Move window (16 kids) | |
2565 | 16.95 1.00 1.00 1.00 22.90 Move window (25 kids) | |
2566 | 16.05 1.01 1.00 1.00 21.32 Move window (50 kids) | |
2567 | 15.58 1.00 0.98 0.98 19.44 Move window (75 kids) | |
2568 | 14.98 1.02 1.03 1.03 18.17 Move window (100 kids) | |
2569 | 10.90 1.01 1.01 1.00 12.68 Move window (200 kids) | |
2570 | 49.42 1.00 1.00 1.00 198.27 Moved unmapped window (4 kids) | |
2571 | 50.72 0.97 1.00 1.00 193.66 Moved unmapped window (16 kids) | |
2572 | 50.87 1.00 0.99 1.00 195.09 Moved unmapped window (25 kids) | |
2573 | 50.72 1.00 1.00 1.00 189.34 Moved unmapped window (50 kids) | |
2574 | 50.87 1.00 1.00 1.00 191.33 Moved unmapped window (75 kids) | |
2575 | 50.87 1.00 1.00 0.90 186.71 Moved unmapped window (100 kids) | |
2576 | 50.87 1.00 1.00 1.00 179.19 Moved unmapped window (200 kids) | |
2577 | 41.04 1.00 1.00 1.00 56.61 Move window via parent (4 kids) | |
2578 | 69.81 1.00 1.00 1.00 130.82 Move window via parent (16 kids) | |
2579 | 95.81 1.00 1.00 1.00 141.92 Move window via parent (25 kids) | |
2580 | 95.98 1.00 1.00 1.00 149.43 Move window via parent (50 kids) | |
2581 | 96.59 1.01 1.01 1.00 153.98 Move window via parent (75 kids) | |
2582 | 97.19 1.00 1.00 1.00 157.30 Move window via parent (100 kids) | |
2583 | 96.67 1.00 0.99 0.96 159.44 Move window via parent (200 kids) | |
2584 | 17.75 1.01 1.00 1.00 27.61 Resize window (4 kids) | |
2585 | 17.94 1.00 1.00 0.99 25.42 Resize window (16 kids) | |
2586 | 17.92 1.01 1.00 1.00 24.47 Resize window (25 kids) | |
2587 | 17.24 0.97 1.00 1.00 24.14 Resize window (50 kids) | |
2588 | 16.81 1.00 1.00 0.99 22.75 Resize window (75 kids) | |
2589 | 16.08 1.00 1.00 1.00 21.20 Resize window (100 kids) | |
2590 | 12.92 1.00 0.99 1.00 16.26 Resize window (200 kids) | |
2591 | 52.94 1.01 1.00 1.00 327.12 Resize unmapped window (4 kids) | |
2592 | 53.60 1.01 1.01 1.01 333.71 Resize unmapped window (16 kids) | |
2593 | 52.99 1.00 1.00 1.00 337.29 Resize unmapped window (25 kids) | |
2594 | 51.98 1.00 1.00 1.00 329.38 Resize unmapped window (50 kids) | |
2595 | 53.05 0.89 1.00 1.00 322.60 Resize unmapped window (75 kids) | |
2596 | 53.05 1.00 1.00 1.00 318.08 Resize unmapped window (100 kids) | |
2597 | 53.11 1.00 1.00 0.99 306.21 Resize unmapped window (200 kids) | |
2598 | 16.76 1.00 0.96 1.00 19.46 Circulate window (4 kids) | |
2599 | 17.24 1.00 1.00 0.97 16.24 Circulate window (16 kids) | |
2600 | 16.30 1.03 1.03 1.03 15.85 Circulate window (25 kids) | |
2601 | 13.45 1.00 1.00 1.00 14.90 Circulate window (50 kids) | |
2602 | 12.91 1.00 1.00 1.00 13.06 Circulate window (75 kids) | |
2603 | 11.30 0.98 1.00 1.00 11.03 Circulate window (100 kids) | |
2604 | 7.58 1.01 1.01 0.99 7.47 Circulate window (200 kids) | |
2605 | 1.01 1.01 0.98 1.00 0.95 Circulate Unmapped window (4 kids) | |
2606 | 1.07 1.07 1.01 1.07 1.02 Circulate Unmapped window (16 kids) | |
2607 | 1.04 1.09 1.06 1.05 0.97 Circulate Unmapped window (25 kids) | |
2608 | 1.04 1.23 1.20 1.18 1.05 Circulate Unmapped window (50 kids) | |
2609 | 1.18 1.53 1.19 1.45 1.24 Circulate Unmapped window (75 kids) | |
2610 | 1.08 1.02 1.01 1.74 1.01 Circulate Unmapped window (100 kids) | |
2611 | 1.01 1.12 0.98 0.91 0.97 Circulate Unmapped window (200 kids) | |
2612 | </screen> | |
2613 | </para> | |
2614 | </sect3> | |
2615 | ||
2616 | <sect3> | |
2617 | <title>Profiling with OProfile</title> | |
2618 | ||
2619 | <para>OProfile (available from http://oprofile.sourceforge.net/) is a | |
2620 | system-wide profiler for Linux systems that uses processor-level | |
2621 | counters to collect sampling data. OProfile can provide information | |
2622 | that is similar to that provided by <command>gprof</command>, but without the | |
2623 | necessity of recompiling the program with special instrumentation (i.e., | |
2624 | OProfile can collect statistical profiling information about optimized | |
2625 | programs). A test harness was developed to collect OProfile data for | |
2626 | each <command>x11perf</command> test individually. | |
2627 | </para> | |
2628 | ||
2629 | <para>Test runs were performed using the RETIRED_INSNS counter on the AMD | |
2630 | Athlon and the CPU_CLK_HALTED counter on the Intel Pentium III (with a | |
2631 | test configuration different from the one described above). We have | |
2632 | examined OProfile output and have compared it with <command>gprof</command> output. | |
2633 | This investigation has not produced results that yield performance | |
2634 | increases in <command>x11perf</command> numbers. | |
2635 | </para> | |
2636 | ||
2637 | </sect3> | |
2638 | ||
2639 | <!-- | |
2640 | <sect3>Retired Instructions | |
2641 | ||
2642 | <p>The initial tests using OProfile were done using the RETIRED_INSNS | |
2643 | counter with DMX running on the dual-processor AMD Athlon machine - the | |
2644 | same test configuration that was described above and that was used for | |
2645 | other tests. The RETIRED_INSNS counter counts retired instructions and | |
2646 | showed drawing, text, copying, and image tests to be dominated (> | |
2647 | 30%) by calls to Hash(), SecurityLookupIDByClass(), | |
2648 | SecurityLookupIDByType(), and StandardReadRequestFromClient(). Some of | |
2649 | these tests also executed significant instructions in | |
2650 | WaitForSomething(). | |
2651 | ||
2652 | <p>In contrast, the window tests executed significant | |
2653 | instructions in SecurityLookupIDByType(), Hash(), | |
2654 | StandardReadRequestFromClient(), but also executed significant | |
2655 | instructions in other routines, such as ConfigureWindow(). Some time | |
2656 | was spent looking at Hash() function, but optimizations in this routine | |
2657 | did not lead to a dramatic increase in <tt/x11perf/ performance. | |
2658 | --> | |
2659 | ||
2660 | <!-- | |
2661 | <sect3>Clock Cycles | |
2662 | ||
2663 | <p>Retired instructions can be misleading because Intel/AMD instructions | |
2664 | execute in variable amounts of time. The OProfile tests were repeated | |
2665 | using the Intel CPU_CLK_HALTED counter with DMX running on the second | |
2666 | back-end machine. Note that this is a different test configuration that | |
2667 | the one described above. However, these tests show the amount of time | |
2668 | (as measured in CPU cycles) that are spent in each routine. Because | |
2669 | <tt/x11perf/ was running on the first back-end machine and because | |
2670 | window optimizations were on, the load on the second back-end machine | |
2671 | was not significant. | |
2672 | ||
2673 | <p>Using CPU_CLK_HALTED, DMX showed simple drawing | |
2674 | tests spending more than 10% of their time in | |
2675 | StandardReadRequestFromClient(), with significant time (> 20% total) | |
2676 | spent in SecurityLookupIDByClass(), WaitForSomething(), and Dispatch(). | |
2677 | For these tests, < 5% of the time was spent in Hash(), which explains | |
2678 | why optimizing the Hash() routine did not impact <tt/x11perf/ results. | |
2679 | ||
2680 | <p>The trapezoid, text, scrolling, copying, and image tests were | |
2681 | dominated by time in ProcFillPoly(), PanoramiXFillPoly(), dmxFillPolygon(), | |
2682 | SecurityLookupIDByClass(), SecurityLookupIDByType(), and | |
2683 | StandardReadRequestFromClient(). Hash() time was generally above 5% but | |
2684 | less than 10% of total time. | |
2685 | --> | |
2686 | ||
2687 | <sect3> | |
2688 | <title>X Test Suite</title> | |
2689 | ||
2690 | <para>The X Test Suite was run on the fully optimized DMX server using the | |
2691 | configuration described above. The following failures were noted: | |
2692 | <screen> | |
2693 | XListPixmapFormats: Test 1 [1] | |
2694 | XChangeWindowAttributes: Test 32 [1] | |
2695 | XCreateWindow: Test 30 [1] | |
2696 | XFreeColors: Test 4 [3] | |
2697 | XCopyArea: Test 13, 17, 21, 25, 30 [2] | |
2698 | XCopyPlane: Test 11, 15, 27, 31 [2] | |
2699 | XSetFontPath: Test 4 [1] | |
2700 | XChangeKeyboardControl: Test 9, 10 [1] | |
2701 | ||
2702 | [1] Previously documented errors expected from the Xinerama | |
2703 | implementation (see Phase I discussion). | |
2704 | [2] Newly noted errors that have been verified as expected | |
2705 | behavior of the Xinerama implementation. | |
2706 | [3] Newly noted error that has been verified as a Xinerama | |
2707 | implementation bug. | |
2708 | </screen> | |
2709 | </para> | |
2710 | ||
2711 | </sect3> | |
2712 | ||
2713 | </sect2> | |
2714 | ||
2715 | <!-- ============================================================ --> | |
2716 | <sect2> | |
2717 | <title>Phase III</title> | |
2718 | ||
2719 | <para>During the third phase of development, support was provided for the | |
2720 | following extensions: SHAPE, RENDER, XKEYBOARD, XInput. | |
2721 | </para> | |
2722 | ||
2723 | <sect3> | |
2724 | <title>SHAPE</title> | |
2725 | ||
2726 | <para>The SHAPE extension is supported. Test applications (e.g., xeyes and | |
2727 | oclock) and window managers that make use of the SHAPE extension will | |
2728 | work as expected. | |
2729 | </para> | |
2730 | </sect3> | |
2731 | ||
2732 | <sect3> | |
2733 | <title>RENDER</title> | |
2734 | ||
2735 | <para>The RENDER extension is supported. The version included in the DMX | |
2736 | CVS tree is version 0.2, and this version is fully supported by Xdmx. | |
2737 | Applications using only version 0.2 functions will work correctly; | |
2738 | however, some apps that make use of functions from later versions do not | |
2739 | properly check the extension's major/minor version numbers. These apps | |
2740 | will fail with a Bad Implementation error when using post-version 0.2 | |
2741 | functions. This is expected behavior. When the DMX CVS tree is updated | |
2742 | to include newer versions of RENDER, support for these newer functions | |
2743 | will be added to the DMX X server. | |
2744 | </para> | |
2745 | </sect3> | |
2746 | ||
2747 | <sect3> | |
2748 | <title>XKEYBOARD</title> | |
2749 | ||
2750 | <para>The XKEYBOARD extension is supported. If present on the back-end X | |
2751 | servers, the XKEYBOARD extension will be used to obtain information | |
2752 | about the type of the keyboard for initialization. Otherwise, the | |
2753 | keyboard will be initialized using defaults. Note that this departs | |
2754 | from older behavior: when Xdmx is compiled without XKEYBOARD support, | |
2755 | the map from the back-end X server will be preserved. With XKEYBOARD | |
2756 | support, the map is not preserved because better information and control | |
2757 | of the keyboard is available. | |
2758 | </para> | |
2759 | </sect3> | |
2760 | ||
2761 | <sect3> | |
2762 | <title>XInput</title> | |
2763 | ||
2764 | <para>The XInput extension is supported. Any device can be used as a core | |
2765 | device and be used as an XInput extension device, with the exception of | |
2766 | core devices on the back-end servers. This limitation is present | |
2767 | because cursor handling on the back-end requires that the back-end | |
2768 | cursor sometimes track the Xdmx core cursor -- behavior that is | |
2769 | incompatible with using the back-end pointer as a non-core device. | |
2770 | </para> | |
2771 | ||
2772 | <para>Currently, back-end extension devices are not available as Xdmx | |
2773 | extension devices, but this limitation should be removed in the future. | |
2774 | </para> | |
2775 | ||
2776 | <para>To demonstrate the XInput extension, and to provide more examples for | |
2777 | low-level input device driver writers, USB device drivers have been | |
2778 | written for mice (usb-mou), keyboards (usb-kbd), and | |
2779 | non-mouse/non-keyboard USB devices (usb-oth). Please see the man page | |
2780 | for information on Linux kernel drivers that are required for using | |
2781 | these Xdmx drivers. | |
2782 | </para> | |
2783 | </sect3> | |
2784 | ||
2785 | <sect3> | |
2786 | <title>DPMS</title> | |
2787 | ||
2788 | <para>The DPMS extension is exported but does not do anything at this time. | |
2789 | </para> | |
2790 | ||
2791 | </sect3> | |
2792 | ||
2793 | <sect3> | |
2794 | <title>Other Extensions</title> | |
2795 | ||
2796 | <para>The LBX, | |
2797 | SECURITY, | |
2798 | XC-APPGROUP, and | |
2799 | XFree86-Bigfont | |
2800 | extensions do not require any special Xdmx support and have been exported. | |
2801 | </para> | |
2802 | ||
2803 | <para>The | |
2804 | BIG-REQUESTS, | |
2805 | DEC-XTRAP, | |
2806 | DOUBLE-BUFFER, | |
2807 | Extended-Visual-Information, | |
2808 | FontCache, | |
2809 | GLX, | |
2810 | MIT-SCREEN-SAVER, | |
2811 | MIT-SHM, | |
2812 | MIT-SUNDRY-NONSTANDARD, | |
2813 | RECORD, | |
2814 | SECURITY, | |
2815 | SGI-GLX, | |
2816 | SYNC, | |
2817 | TOG-CUP, | |
2818 | X-Resource, | |
2819 | XC-MISC, | |
2820 | XFree86-DGA, | |
2821 | XFree86-DRI, | |
2822 | XFree86-Misc, | |
2823 | XFree86-VidModeExtension, and | |
2824 | XVideo | |
2825 | extensions are <emphasis remap="it">not</emphasis> supported at this time, but will be evaluated | |
2826 | for inclusion in future DMX releases. <emphasis remap="bf">See below for additional work | |
2827 | on extensions after Phase III.</emphasis> | |
2828 | </para> | |
2829 | </sect3> | |
2830 | </sect2> | |
2831 | ||
2832 | <sect2> | |
2833 | <title>Phase IV</title> | |
2834 | ||
2835 | <sect3> | |
2836 | <title>Moving to XFree86 4.3.0</title> | |
2837 | ||
2838 | <para>For Phase IV, the recent release of XFree86 4.3.0 (27 February 2003) | |
2839 | was merged onto the dmx.sourceforge.net CVS trunk and all work is | |
2840 | proceeding using this tree. | |
2841 | </para> | |
2842 | </sect3> | |
2843 | ||
2844 | <sect3> | |
2845 | <title>Extensions </title> | |
2846 | ||
2847 | <sect4> | |
2848 | <title>XC-MISC (supported)</title> | |
2849 | ||
2850 | <para>XC-MISC is used internally by the X library to recycle XIDs from the | |
2851 | X server. This is important for long-running X server sessions. Xdmx | |
2852 | supports this extension. The X Test Suite passed and failed the exact | |
2853 | same tests before and after this extension was enabled. | |
2854 | <!-- Tested February/March 2003 --> | |
2855 | </para> | |
2856 | </sect4> | |
2857 | ||
2858 | <sect4> | |
2859 | <title>Extended-Visual-Information (supported)</title> | |
2860 | ||
2861 | <para>The Extended-Visual-Information extension provides a method for an X | |
2862 | client to obtain detailed visual information. Xdmx supports this | |
2863 | extension. It was tested using the <filename>hw/dmx/examples/evi</filename> example | |
2864 | program. <emphasis remap="bf">Note that this extension is not Xinerama-aware</emphasis> -- it will | |
2865 | return visual information for each screen even though Xinerama is | |
2866 | causing the X server to export a single logical screen. | |
2867 | <!-- Tested March 2003 --> | |
2868 | </para> | |
2869 | </sect4> | |
2870 | ||
2871 | <sect4> | |
2872 | <title>RES (supported)</title> | |
2873 | ||
2874 | <para>The X-Resource extension provides a mechanism for a client to obtain | |
2875 | detailed information about the resources used by other clients. This | |
2876 | extension was tested with the <filename>hw/dmx/examples/res</filename> program. The | |
2877 | X Test Suite passed and failed the exact same tests before and after | |
2878 | this extension was enabled. | |
2879 | <!-- Tested March 2003 --> | |
2880 | </para> | |
2881 | </sect4> | |
2882 | ||
2883 | <sect4> | |
2884 | <title>BIG-REQUESTS (supported)</title> | |
2885 | ||
2886 | <para>This extension enables the X11 protocol to handle requests longer | |
2887 | than 262140 bytes. The X Test Suite passed and failed the exact same | |
2888 | tests before and after this extension was enabled. | |
2889 | <!-- Tested March 2003 --> | |
2890 | </para> | |
2891 | </sect4> | |
2892 | ||
2893 | <sect4> | |
2894 | <title>XSYNC (supported)</title> | |
2895 | ||
2896 | <para>This extension provides facilities for two different X clients to | |
2897 | synchronize their requests. This extension was minimally tested with | |
2898 | <command>xdpyinfo</command> and the X Test Suite passed and failed the exact same | |
2899 | tests before and after this extension was enabled. | |
2900 | <!-- Tested March 2003 --> | |
2901 | </para> | |
2902 | </sect4> | |
2903 | ||
2904 | <sect4> | |
2905 | <title>XTEST, RECORD, DEC-XTRAP (supported) and XTestExtension1 (not supported)</title> | |
2906 | ||
2907 | <para>The XTEST and RECORD extension were developed by the X Consortium for | |
2908 | use in the X Test Suite and are supported as a standard in the X11R6 | |
2909 | tree. They are also supported in Xdmx. When X Test Suite tests that | |
2910 | make use of the XTEST extension are run, Xdmx passes and fails exactly | |
2911 | the same tests as does a standard XFree86 X server. When the | |
2912 | <literal remap="tt">rcrdtest</literal> test (a part of the X Test Suite that verifies the RECORD | |
2913 | extension) is run, Xdmx passes and fails exactly the same tests as does | |
2914 | a standard XFree86 X server. <!-- Tested February/March 2003 --> | |
2915 | </para> | |
2916 | ||
2917 | <para>There are two older XTEST-like extensions: DEC-XTRAP and | |
2918 | XTestExtension1. The XTestExtension1 extension was developed for use by | |
2919 | the X Testing Consortium for use with a test suite that eventually | |
2920 | became (part of?) the X Test Suite. Unlike XTEST, which only allows | |
2921 | events to be sent to the server, the XTestExtension1 extension also | |
2922 | allowed events to be recorded (similar to the RECORD extension). The | |
2923 | second is the DEC-XTRAP extension that was developed by the Digital | |
2924 | Equipment Corporation. | |
2925 | </para> | |
2926 | ||
2927 | <para>The DEC-XTRAP extension is available from Xdmx and has been tested | |
2928 | with the <command>xtrap*</command> tools which are distributed as standard X11R6 | |
2929 | clients. <!-- Tested March 2003 --> | |
2930 | </para> | |
2931 | ||
2932 | <para>The XTestExtension1 is <emphasis>not</emphasis> supported because it does not appear | |
2933 | to be used by any modern X clients (the few that support it also support | |
2934 | XTEST) and because there are no good methods available for testing that | |
2935 | it functions correctly (unlike XTEST and DEC-XTRAP, the code for | |
2936 | XTestExtension1 is not part of the standard X server source tree, so | |
2937 | additional testing is important). <!-- Tested March 2003 --> | |
2938 | </para> | |
2939 | ||
2940 | <para>Most of these extensions are documented in the X11R6 source tree. | |
2941 | Further, several original papers exist that this author was unable to | |
2942 | locate -- for completeness and historical interest, citations are | |
2943 | provide: | |
2944 | <variablelist> | |
2945 | <varlistentry> | |
2946 | <term>XRECORD</term> | |
2947 | <listitem> | |
2948 | <para>Martha Zimet. Extending X For Recording. 8th Annual X | |
2949 | Technical Conference Boston, MA January 24-26, 1994. | |
2950 | </para></listitem></varlistentry> | |
2951 | <varlistentry> | |
2952 | <term>DEC-XTRAP</term> | |
2953 | <listitem> | |
2954 | <para>Dick Annicchiarico, Robert Chesler, Alan Jamison. XTrap | |
2955 | Architecture. Digital Equipment Corporation, July 1991. | |
2956 | </para></listitem></varlistentry> | |
2957 | <varlistentry> | |
2958 | <term>XTestExtension1</term> | |
2959 | <listitem> | |
2960 | <para>Larry Woestman. X11 Input Synthesis Extension | |
2961 | Proposal. Hewlett Packard, November 1991. | |
2962 | </para></listitem></varlistentry> | |
2963 | </variablelist> | |
2964 | </para> | |
2965 | </sect4> | |
2966 | ||
2967 | <sect4> | |
2968 | <title>MIT-MISC (not supported)</title> | |
2969 | ||
2970 | <para>The MIT-MISC extension is used to control a bug-compatibility flag | |
2971 | that provides compatibility with xterm programs from X11R1 and X11R2. | |
2972 | There does not appear to be a single client available that makes use of | |
2973 | this extension and there is not way to verify that it works correctly. | |
2974 | The Xdmx server does <emphasis>not</emphasis> support MIT-MISC. | |
2975 | </para> | |
2976 | </sect4> | |
2977 | ||
2978 | <sect4> | |
2979 | <title>SCREENSAVER (not supported)</title> | |
2980 | ||
2981 | <para>This extension provides special support for the X screen saver. It | |
2982 | was tested with beforelight, which appears to be the only client that | |
2983 | works with it. When Xinerama was not active, <command>beforelight</command> behaved | |
2984 | as expected. However, when Xinerama was active, <command>beforelight</command> did | |
2985 | not behave as expected. Further, when this extension is not active, | |
2986 | <command>xscreensaver</command> (a widely-used X screen saver program) did not behave | |
2987 | as expected. Since this extension is not Xinerama-aware and is not | |
2988 | commonly used with expected results by clients, we have left this | |
2989 | extension disabled at this time. | |
2990 | </para> | |
2991 | </sect4> | |
2992 | ||
2993 | <sect4> | |
2994 | <title>GLX (supported)</title> | |
2995 | ||
2996 | <para>The GLX extension provides OpenGL and GLX windowing support. In | |
2997 | Xdmx, the extension is called glxProxy, and it is Xinerama aware. It | |
2998 | works by either feeding requests forward through Xdmx to each of the | |
2999 | back-end servers or handling them locally. All rendering requests are | |
3000 | handled on the back-end X servers. This code was donated to the DMX | |
3001 | project by SGI. For the X Test Suite results comparison, see below. | |
3002 | </para> | |
3003 | </sect4> | |
3004 | ||
3005 | <sect4> | |
3006 | <title>RENDER (supported)</title> | |
3007 | ||
3008 | <para>The X Rendering Extension (RENDER) provides support for digital image | |
3009 | composition. Geometric and text rendering are supported. RENDER is | |
3010 | partially Xinerama-aware, with text and the most basic compositing | |
3011 | operator; however, its higher level primitives (triangles, triangle | |
3012 | strips, and triangle fans) are not yet Xinerama-aware. The RENDER | |
3013 | extension is still under development, and is currently at version 0.8. | |
3014 | Additional support will be required in DMX as more primitives and/or | |
3015 | requests are added to the extension. | |
3016 | </para> | |
3017 | ||
3018 | <para>There is currently no test suite for the X Rendering Extension; | |
3019 | however, there has been discussion of developing a test suite as the | |
3020 | extension matures. When that test suite becomes available, additional | |
3021 | testing can be performed with Xdmx. The X Test Suite passed and failed | |
3022 | the exact same tests before and after this extension was enabled. | |
3023 | </para> | |
3024 | </sect4> | |
3025 | ||
3026 | <sect4> | |
3027 | <title>Summary</title> | |
3028 | ||
3029 | <!-- WARNING: this list is duplicated in the "Common X extension | |
3030 | support" section --> | |
3031 | <para>To summarize, the following extensions are currently supported: | |
3032 | BIG-REQUESTS, | |
3033 | DEC-XTRAP, | |
3034 | DMX, | |
3035 | DPMS, | |
3036 | Extended-Visual-Information, | |
3037 | GLX, | |
3038 | LBX, | |
3039 | RECORD, | |
3040 | RENDER, | |
3041 | SECURITY, | |
3042 | SHAPE, | |
3043 | SYNC, | |
3044 | X-Resource, | |
3045 | XC-APPGROUP, | |
3046 | XC-MISC, | |
3047 | XFree86-Bigfont, | |
3048 | XINERAMA, | |
3049 | XInputExtension, | |
3050 | XKEYBOARD, and | |
3051 | XTEST. | |
3052 | </para> | |
3053 | ||
3054 | <para>The following extensions are <emphasis>not</emphasis> supported at this time: | |
3055 | DOUBLE-BUFFER, | |
3056 | FontCache, | |
3057 | MIT-SCREEN-SAVER, | |
3058 | MIT-SHM, | |
3059 | MIT-SUNDRY-NONSTANDARD, | |
3060 | TOG-CUP, | |
3061 | XFree86-DGA, | |
3062 | XFree86-Misc, | |
3063 | XFree86-VidModeExtension, | |
3064 | XTestExtensionExt1, and | |
3065 | XVideo. | |
3066 | </para> | |
3067 | </sect4> | |
3068 | </sect3> | |
3069 | ||
3070 | <sect3> | |
3071 | <title>Additional Testing with the X Test Suite</title> | |
3072 | ||
3073 | <sect4> | |
3074 | <title>XFree86 without XTEST</title> | |
3075 | ||
3076 | <para>After the release of XFree86 4.3.0, we retested the XFree86 X server | |
3077 | with and without using the XTEST extension. When the XTEST extension | |
3078 | was <emphasis>not</emphasis> used for testing, the XFree86 4.3.0 server running on our | |
3079 | usual test system with a Radeon VE card reported unexpected failures in | |
3080 | the following tests: | |
3081 | <literallayout> | |
3082 | XListPixmapFormats: Test 1 | |
3083 | XChangeKeyboardControl: Tests 9, 10 | |
3084 | XGetDefault: Test 5 | |
3085 | XRebindKeysym: Test 1 | |
3086 | </literallayout> | |
3087 | </para> | |
3088 | </sect4> | |
3089 | ||
3090 | <sect4> | |
3091 | <title>XFree86 with XTEST</title> | |
3092 | ||
3093 | <para>When using the XTEST extension, the XFree86 4.3.0 server reported the | |
3094 | following errors: | |
3095 | <literallayout> | |
3096 | XListPixmapFormats: Test 1 | |
3097 | XChangeKeyboardControl: Tests 9, 10 | |
3098 | XGetDefault: Test 5 | |
3099 | XRebindKeysym: Test 1 | |
3100 | ||
3101 | XAllowEvents: Tests 20, 21, 24 | |
3102 | XGrabButton: Tests 5, 9-12, 14, 16, 19, 21-25 | |
3103 | XGrabKey: Test 8 | |
3104 | XSetPointerMapping: Test 3 | |
3105 | XUngrabButton: Test 4 | |
3106 | </literallayout> | |
3107 | </para> | |
3108 | ||
3109 | <para>While these errors may be important, they will probably be fixed | |
3110 | eventually in the XFree86 source tree. We are particularly interested | |
3111 | in demonstrating that the Xdmx server does not introduce additional | |
3112 | failures that are not known Xinerama failures. | |
3113 | </para> | |
3114 | </sect4> | |
3115 | ||
3116 | <sect4> | |
3117 | <title>Xdmx with XTEST, without Xinerama, without GLX</title> | |
3118 | ||
3119 | <para>Without Xinerama, but using the XTEST extension, the following errors | |
3120 | were reported from Xdmx (note that these are the same as for the XFree86 | |
3121 | 4.3.0, except that XGetDefault no longer fails): | |
3122 | <literallayout> | |
3123 | XListPixmapFormats: Test 1 | |
3124 | XChangeKeyboardControl: Tests 9, 10 | |
3125 | XRebindKeysym: Test 1 | |
3126 | ||
3127 | XAllowEvents: Tests 20, 21, 24 | |
3128 | XGrabButton: Tests 5, 9-12, 14, 16, 19, 21-25 | |
3129 | XGrabKey: Test 8 | |
3130 | XSetPointerMapping: Test 3 | |
3131 | XUngrabButton: Test 4 | |
3132 | </literallayout> | |
3133 | </para> | |
3134 | </sect4> | |
3135 | ||
3136 | <sect4> | |
3137 | <title>Xdmx with XTEST, with Xinerama, without GLX</title> | |
3138 | ||
3139 | <para>With Xinerama, using the XTEST extension, the following errors | |
3140 | were reported from Xdmx: | |
3141 | <literallayout> | |
3142 | XListPixmapFormats: Test 1 | |
3143 | XChangeKeyboardControl: Tests 9, 10 | |
3144 | XRebindKeysym: Test 1 | |
3145 | ||
3146 | XAllowEvents: Tests 20, 21, 24 | |
3147 | XGrabButton: Tests 5, 9-12, 14, 16, 19, 21-25 | |
3148 | XGrabKey: Test 8 | |
3149 | XSetPointerMapping: Test 3 | |
3150 | XUngrabButton: Test 4 | |
3151 | ||
3152 | XCopyPlane: Tests 13, 22, 31 (well-known XTEST/Xinerama interaction issue) | |
3153 | XDrawLine: Test 67 | |
3154 | XDrawLines: Test 91 | |
3155 | XDrawSegments: Test 68 | |
3156 | </literallayout> | |
3157 | Note that the first two sets of errors are the same as for the XFree86 | |
3158 | 4.3.0 server, and that the XCopyPlane error is a well-known error | |
3159 | resulting from an XTEST/Xinerama interaction when the request crosses a | |
3160 | screen boundary. The XDraw* errors are resolved when the tests are run | |
3161 | individually and they do not cross a screen boundary. We will | |
3162 | investigate these errors further to determine their cause. | |
3163 | </para> | |
3164 | </sect4> | |
3165 | ||
3166 | <sect4> | |
3167 | <title>Xdmx with XTEST, with Xinerama, with GLX</title> | |
3168 | ||
3169 | <para>With GLX enabled, using the XTEST extension, the following errors | |
3170 | were reported from Xdmx (these results are from early during the Phase | |
3171 | IV development, but were confirmed with a late Phase IV snapshot): | |
3172 | <literallayout> | |
3173 | XListPixmapFormats: Test 1 | |
3174 | XChangeKeyboardControl: Tests 9, 10 | |
3175 | XRebindKeysym: Test 1 | |
3176 | ||
3177 | XAllowEvents: Tests 20, 21, 24 | |
3178 | XGrabButton: Tests 5, 9-12, 14, 16, 19, 21-25 | |
3179 | XGrabKey: Test 8 | |
3180 | XSetPointerMapping: Test 3 | |
3181 | XUngrabButton: Test 4 | |
3182 | ||
3183 | XClearArea: Test 8 | |
3184 | XCopyArea: Tests 4, 5, 11, 14, 17, 23, 25, 27, 30 | |
3185 | XCopyPlane: Tests 6, 7, 10, 19, 22, 31 | |
3186 | XDrawArcs: Tests 89, 100, 102 | |
3187 | XDrawLine: Test 67 | |
3188 | XDrawSegments: Test 68 | |
3189 | </literallayout> | |
3190 | Note that the first two sets of errors are the same as for the XFree86 | |
3191 | 4.3.0 server, and that the third set has different failures than when | |
3192 | Xdmx does not include GLX support. Since the GLX extension adds new | |
3193 | visuals to support GLX's visual configs and the X Test Suite runs tests | |
3194 | over the entire set of visuals, additional rendering tests were run and | |
3195 | presumably more of them crossed a screen boundary. This conclusion is | |
3196 | supported by the fact that nearly all of the rendering errors reported | |
3197 | are resolved when the tests are run individually and they do no cross a | |
3198 | screen boundary. | |
3199 | </para> | |
3200 | ||
3201 | <para>Further, when hardware rendering is disabled on the back-end displays, | |
3202 | many of the errors in the third set are eliminated, leaving only: | |
3203 | <literallayout> | |
3204 | XClearArea: Test 8 | |
3205 | XCopyArea: Test 4, 5, 11, 14, 17, 23, 25, 27, 30 | |
3206 | XCopyPlane: Test 6, 7, 10, 19, 22, 31 | |
3207 | </literallayout> | |
3208 | </para> | |
3209 | </sect4> | |
3210 | ||
3211 | <sect4> | |
3212 | <title>Conclusion</title> | |
3213 | ||
3214 | <para>We conclude that all of the X Test Suite errors reported for Xdmx are | |
3215 | the result of errors in the back-end X server or the Xinerama | |
3216 | implementation. Further, all of these errors that can be reasonably | |
3217 | fixed at the Xdmx layer have been. (Where appropriate, we have | |
3218 | submitted patches to the XFree86 and Xinerama upstream maintainers.) | |
3219 | </para> | |
3220 | </sect4> | |
3221 | </sect3> | |
3222 | ||
3223 | <sect3> | |
3224 | <title>Dynamic Reconfiguration</title> | |
3225 | ||
3226 | <para>During this development phase, dynamic reconfiguration support was | |
3227 | added to DMX. This support allows an application to change the position | |
3228 | and offset of a back-end server's screen. For example, if the | |
3229 | application would like to shift a screen slightly to the left, it could | |
3230 | query Xdmx for the screen's <x,y> position and then dynamically | |
3231 | reconfigure that screen to be at position <x+10,y>. When a screen | |
3232 | is dynamically reconfigured, input handling and a screen's root window | |
3233 | dimensions are adjusted as needed. These adjustments are transparent to | |
3234 | the user. | |
3235 | </para> | |
3236 | ||
3237 | <sect4> | |
3238 | <title>Dynamic reconfiguration extension</title> | |
3239 | ||
3240 | <para>The application interface to DMX's dynamic reconfiguration is through | |
3241 | a function in the DMX extension library: | |
3242 | <programlisting> | |
3243 | Bool DMXReconfigureScreen(Display *dpy, int screen, int x, int y) | |
3244 | </programlisting> | |
3245 | where <parameter>dpy</parameter> is DMX server's display, <parameter>screen</parameter> is the number of the | |
3246 | screen to be reconfigured, and <parameter>x</parameter> and <parameter>y</parameter> are the new upper, | |
3247 | left-hand coordinates of the screen to be reconfigured. | |
3248 | </para> | |
3249 | ||
3250 | <para>The coordinates are not limited other than as required by the X | |
3251 | protocol, which limits all coordinates to a signed 16 bit number. In | |
3252 | addition, all coordinates within a screen must also be legal values. | |
3253 | Therefore, setting a screen's upper, left-hand coordinates such that the | |
3254 | right or bottom edges of the screen is greater than 32,767 is illegal. | |
3255 | </para> | |
3256 | </sect4> | |
3257 | ||
3258 | <sect4> | |
3259 | <title>Bounding box</title> | |
3260 | ||
3261 | <para>When the Xdmx server is started, a bounding box is calculated from | |
3262 | the screens' layout given either on the command line or in the | |
3263 | configuration file. This bounding box is currently fixed for the | |
3264 | lifetime of the Xdmx server. | |
3265 | </para> | |
3266 | ||
3267 | <para>While it is possible to move a screen outside of the bounding box, it | |
3268 | is currently not possible to change the dimensions of the bounding box. | |
3269 | For example, it is possible to specify coordinates of <-100,-100> | |
3270 | for the upper, left-hand corner of the bounding box, which was | |
3271 | previously at coordinates <0,0>. As expected, the screen is moved | |
3272 | down and to the right; however, since the bounding box is fixed, the | |
3273 | left side and upper portions of the screen exposed by the | |
3274 | reconfiguration are no longer accessible on that screen. Those | |
3275 | inaccessible regions are filled with black. | |
3276 | </para> | |
3277 | ||
3278 | <para>This fixed bounding box limitation will be addressed in a future | |
3279 | development phase. | |
3280 | </para> | |
3281 | </sect4> | |
3282 | ||
3283 | <sect4> | |
3284 | <title>Sample applications</title> | |
3285 | ||
3286 | <para>An example of where this extension is useful is in setting up a video | |
3287 | wall. It is not always possible to get everything perfectly aligned, | |
3288 | and sometimes the positions are changed (e.g., someone might bump into a | |
3289 | projector). Instead of physically moving projectors or monitors, it is | |
3290 | now possible to adjust the positions of the back-end server's screens | |
3291 | using the dynamic reconfiguration support in DMX. | |
3292 | </para> | |
3293 | ||
3294 | <para>Other applications, such as automatic setup and calibration tools, | |
3295 | can make use of dynamic reconfiguration to correct for projector | |
3296 | alignment problems, as long as the projectors are still arranged | |
3297 | rectilinearly. Horizontal and vertical keystone correction could be | |
3298 | applied to projectors to correct for non-rectilinear alignment problems; | |
3299 | however, this must be done external to Xdmx. | |
3300 | </para> | |
3301 | ||
3302 | <para>A sample test program is included in the DMX server's examples | |
3303 | directory to demonstrate the interface and how an application might use | |
3304 | dynamic reconfiguration. See <filename>dmxreconfig.c</filename> for details. | |
3305 | </para> | |
3306 | </sect4> | |
3307 | ||
3308 | <sect4> | |
3309 | <title>Additional notes</title> | |
3310 | ||
3311 | <para>In the original development plan, Phase IV was primarily devoted to | |
3312 | adding OpenGL support to DMX; however, SGI became interested in the DMX | |
3313 | project and developed code to support OpenGL/GLX. This code was later | |
3314 | donated to the DMX project and integrated into the DMX code base, which | |
3315 | freed the DMX developers to concentrate on dynamic reconfiguration (as | |
3316 | described above). | |
3317 | </para> | |
3318 | </sect4> | |
3319 | </sect3> | |
3320 | ||
3321 | <sect3> | |
3322 | <title>Doxygen documentation</title> | |
3323 | ||
3324 | <para>Doxygen is an open-source (GPL) documentation system for generating | |
3325 | browseable documentation from stylized comments in the source code. We | |
3326 | have placed all of the Xdmx server and DMX protocol source code files | |
3327 | under Doxygen so that comprehensive documentation for the Xdmx source | |
3328 | code is available in an easily browseable format. | |
3329 | </para> | |
3330 | </sect3> | |
3331 | ||
3332 | <sect3> | |
3333 | <title>Valgrind</title> | |
3334 | ||
3335 | <para>Valgrind, an open-source (GPL) memory debugger for Linux, was used to | |
3336 | search for memory management errors. Several memory leaks were detected | |
3337 | and repaired. The following errors were not addressed: | |
3338 | <orderedlist> | |
3339 | <listitem><para> | |
3340 | When the X11 transport layer sends a reply to the client, only | |
3341 | those fields that are required by the protocol are filled in -- | |
3342 | unused fields are left as uninitialized memory and are therefore | |
3343 | noted by valgrind. These instances are not errors and were not | |
3344 | repaired. | |
3345 | </para></listitem> | |
3346 | <listitem><para> | |
3347 | At each server generation, glxInitVisuals allocates memory that | |
3348 | is never freed. The amount of memory lost each generation | |
3349 | approximately equal to 128 bytes for each back-end visual. | |
3350 | Because the code involved is automatically generated, this bug | |
3351 | has not been fixed and will be referred to SGI. | |
3352 | </para></listitem> | |
3353 | <listitem><para> | |
3354 | At each server generation, dmxRealizeFont calls XLoadQueryFont, | |
3355 | which allocates a font structure that is not freed. | |
3356 | dmxUnrealizeFont can free the font structure for the first | |
3357 | screen, but cannot free it for the other screens since they are | |
3358 | already closed by the time dmxUnrealizeFont could free them. | |
3359 | The amount of memory lost each generation is approximately equal | |
3360 | to 80 bytes per font per back-end. When this bug is fixed in | |
3361 | the the X server's device-independent (dix) code, DMX will be | |
3362 | able to properly free the memory allocated by XLoadQueryFont. | |
3363 | </para></listitem> | |
3364 | </orderedlist> | |
3365 | </para> | |
3366 | </sect3> | |
3367 | ||
3368 | <sect3> | |
3369 | <title>RATS</title> | |
3370 | ||
3371 | <para>RATS (Rough Auditing Tool for Security) is an open-source (GPL) | |
3372 | security analysis tool that scans source code for common | |
3373 | security-related programming errors (e.g., buffer overflows and TOCTOU | |
3374 | races). RATS was used to audit all of the code in the hw/dmx directory | |
3375 | and all "High" notations were checked manually. The code was either | |
3376 | re-written to eliminate the warning, or a comment containing "RATS" was | |
3377 | inserted on the line to indicate that a human had checked the code. | |
3378 | Unrepaired warnings are as follows: | |
3379 | <orderedlist> | |
3380 | <listitem><para> | |
3381 | Fixed-size buffers are used in many areas, but code has been | |
3382 | added to protect against buffer overflows (e.g., snprintf). | |
3383 | The only instances that have not yet been fixed are in | |
3384 | config/xdmxconfig.c (which is not part of the Xdmx server) and | |
3385 | input/usb-common.c. | |
3386 | </para></listitem> | |
3387 | <listitem><para> | |
3388 | vprintf and vfprintf are used in the logging routines. In | |
3389 | general, all uses of these functions (e.g., dmxLog) provide a | |
3390 | constant format string from a trusted source, so the use is | |
3391 | relatively benign. | |
3392 | </para></listitem> | |
3393 | <listitem><para> | |
3394 | glxProxy/glxscreens.c uses getenv and strcat. The use of these | |
3395 | functions is safe and will remain safe as long as | |
3396 | ExtensionsString is longer then GLXServerExtensions (ensuring | |
3397 | this may not be ovious to the casual programmer, but this is in | |
3398 | automatically generated code, so we hope that the generator | |
3399 | enforces this constraint). | |
3400 | </para></listitem> | |
3401 | </orderedlist> | |
3402 | ||
3403 | </para> | |
3404 | ||
3405 | </sect3> | |
3406 | ||
3407 | </sect2> | |
3408 | ||
3409 | </sect1> | |
3410 | ||
3411 | </appendix> | |
3412 | ||
3413 | </article> | |
3414 | ||
3415 | <!-- Local Variables: --> | |
3416 | <!-- fill-column: 72 --> | |
3417 | <!-- End: --> |