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Platform/GFX/OffMainThreadCompositing (view source)
Revision as of 15:05, 22 June 2013
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=Current status= | =Current status= | ||
Shipped on Android and FirefoxOS. | |||
Usable on Linux and Mac (buggy and off by default). | |||
Work in progress on Windows. | |||
=Goals= | =Goals= | ||
The main goal is to improve responsiveness. | The main goal is to improve responsiveness. this architecture has the following advantages over our on-the-main-thread approach: | ||
* Reduce main thread contention | * Reduce main thread contention | ||
* Asynchronous scrolling | * Asynchronous scrolling | ||
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=Design= | =Design= | ||
[[File: | [[File:LayersRefactoring.png|thumb|650px|Gfx layers class diagram]] | ||
A new thread will handle composition. This thread will receive updates from the content thread, much as the chrome process receives updates from the content process in e10s. Indeed, as much as possible, the shadow layers machinery developed for e10s will be adapted for off-main-thread compositing. The design may need to diverge in some places from the e10s approach: for example, on Android, updates from the content thread to the compositing thread need to be asynchronous. ('''note''': With the current code ... this might not be the case with the new frontend, and even in the current code, the cases that require async PLayers could be fixed at the widget/android level too. We'll need to make a tradeoff.) | A new thread will handle composition. This thread will receive updates from the content thread, much as the chrome process receives updates from the content process in e10s. Indeed, as much as possible, the shadow layers machinery developed for e10s will be adapted for off-main-thread compositing. The design may need to diverge in some places from the e10s approach: for example, on Android, updates from the content thread to the compositing thread need to be asynchronous. ('''note''': With the current code ... this might not be the case with the new frontend, and even in the current code, the cases that require async PLayers could be fixed at the widget/android level too. We'll need to make a tradeoff.) | ||
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=Plan= | =Plan= | ||
Our highest priority platform for this project has been | Our highest priority platform for this project has been mobile platforms, but we want to extend this to all supported platforms: Mac, Windows (D3D9 + D3D10), Linux, and software-only (BasicLayers; possibly, there is ongoing discussion as to whether this is the best use of resources to improve the experience for 'low-end' users). | ||
==Current status== | ==Current status== | ||
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* Only scrolling is asynchronous/off main thread. All other features require further work. | * Only scrolling is asynchronous/off main thread. All other features require further work. | ||
=== Operating systems === | === Operating systems === | ||
* Android: Released. We continue to iron out OMTC bugs as the | * Android and B2G: Released. We continue to iron out OMTC bugs as the test base expands, but we are already quite high-quality. | ||
* OS X: {{bug|756601}} Alpha quality. We began development of OMTC on this platform, but we haven't worked on it much since then. It pretty much works but is disabled by default. | * OS X: {{bug|756601}} Alpha quality. We began development of OMTC on this platform, but we haven't worked on it much since then. It pretty much works but is disabled by default. | ||
* Linux: {{bug|722012}} In initial implementation stages. We're still sorting out basic issues with X and GL, as we don't support OMTC with BasicLayers yet. | * Linux: {{bug|722012}} In initial implementation stages. We're still sorting out basic issues with X and GL, as we don't support OMTC with BasicLayers yet. | ||
* BasicLayers (software only): {{bug|703484}} In initial implementation stages. Marco Castelluccio, a volunteer contributor, is working through implementing off-main-thread BasicLayers, which also involves making our Cairo library thread-safe. | * BasicLayers (software only): {{bug|703484}} In initial implementation stages. Marco Castelluccio, a volunteer contributor, is working through implementing off-main-thread BasicLayers, which also involves making our Cairo library thread-safe. | ||
* Windows: | * Windows: | ||
** Direct3D 10: {{bug|756606}} | ** Direct3D 10: {{bug|756606}} Work in progress; has some fundamental problems with textures which require the layers refactoring. | ||
** Direct3D 9: {{bug|756608}} | ** Direct3D 9: {{bug|756608}} Work in progress; but, in theory, should be fairly straightforward (there are already shadow layers implemented, but I don't think they are used anywhere). | ||
==Future Work== | ==Future Work== | ||
===WebGL=== | ===WebGL=== | ||
The WebGL streaming buffer project helped improve our WebGL compositing performances. | |||
* Sharing WebGL backing textures between threads {{bug|728524}} | Even though there is stil some work in progress, most of the work has landed already. | ||
* Double-buffering WebGL {{bug|716859}} | * Sharing WebGL backing textures between threads {{bug|728524}} lets us avoid reading back. | ||
* Double-buffering WebGL {{bug|716859}} lets us hand off a texture to the compositor, then go back to drawing to the WebGL context. | |||
* Not using glFinish() to synchronize between threads {{bug|697831}} (most likely using the ARB_sync extension) will let us hand those textures off faster. | * Not using glFinish() to synchronize between threads {{bug|697831}} (most likely using the ARB_sync extension) will let us hand those textures off faster. | ||
'''Assignee''': Cody Brocious (Daeken)<br> | '''Assignee''': Jeff Giblert, Cody Brocious (Daeken)<br> | ||
'''Status''': | '''Status''': Mostly done | ||
===Video=== | ===Video=== | ||
The video pipeline can now decode and composite video frames without touching the content thread (async-video). To improve performances and audio/video synchronization, there is some work in adding synchronization logic on the compositor side. | |||
* Asynchronous video composition is {{bug|706172}} | * Asynchronous video composition (already landed) is {{bug|706172}} | ||
'''Assignee''': Nicolas Silva (nical)<br> | '''Assignee''': Nicolas Silva (nical)<br> | ||
'''Status''': | '''Status''': async-video done, improvements planned. | ||
===CSS Animations=== | ===CSS Animations=== | ||
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* {{bug|717872}} | * {{bug|717872}} | ||
'''Assignee''': | '''Assignee''': Joe Drew <br> | ||
'''Status''': | '''Status''': Work in progress | ||
===Off-main-thread layers implementations=== | ===Off-main-thread layers implementations=== | ||
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==== Layers refactoring ==== | ==== Layers refactoring ==== | ||
The layers system has been heavily refactored to more easily facilitate OMTC on all platforms. | |||
The biggest changes are to the compositing side, and to how textures/buffers/handles are passed between the drawing and compositing components. The aim is for most OMTC code to be backend-independent. Compositing is done by a Compositor class (rather than the ShadowLayerManager, which still have responsibility for managing the shadow layer tree). There are backend-specific compositor sub-classes, but the shadow layer tree and it's manager are backend-independent. Buffers/textures are handled by TextureClient/TextureHost pairs which have backend-specific subclasses and handle all inter-thread communication. The layer classes can then be agnostic about backend and IPC mechanism. | |||
The [https://wiki.mozilla.org/Gecko:Overview#Graphics Gecko overview] wiki page contains good documentation about the current (post refactoring) layers system. | |||
==== Android ==== | ==== Android ==== | ||
'''Assignee''': Benoit Girard/Ali Juma<br> | '''Assignee''': Benoit Girard/Ali Juma<br> | ||
'''Status''': | '''Status''': Shipped | ||
==== Mac OS X ==== | ==== Mac OS X ==== | ||
'''Assignee''': UNASSIGNED<br> | '''Assignee''': UNASSIGNED<br> | ||
'''Status''': | '''Status''': Beta quality | ||
==== Linux ==== | ==== Linux ==== | ||
'''Assignee''': Nicolas Silva<br> | '''Assignee''': Nicolas Silva<br> | ||
'''Status''': In development | '''Status''': In development, testable but buggy not optimized. | ||
==== Direct3D 9 ==== | ==== Direct3D 9 ==== | ||
'''Assignee''': | '''Assignee''': Nick Cameron<br> | ||
'''Status''': | '''Status''': In development | ||
==== Direct3D 10 ==== | ==== Direct3D 10 ==== | ||
'''Assignee''': | '''Assignee''': Bas Schouten<br> | ||
'''Status''': | '''Status''': Alpha quality | ||
==== Basic (Software-only) ==== | ==== Basic (Software-only) ==== | ||
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=Development= | =Development= | ||
Development is happening on mozilla-central | Development is happening on mozilla-central. | ||
=Test cases= | =Test cases= | ||
http://people.mozilla.com/~ajuma/omtc/ | http://people.mozilla.com/~ajuma/omtc/ | ||