257644 2023-06-02 04:36:06 -0700 GPUP WebGL flush() and finish() are asynchronous 2023-06-28 22:46:01 -0700 1 1 1 Unclassified WebKit WebGL WebKit Local Build Unspecified Unspecified NEW https://bugs.webkit.org/show_bug.cgi?id=252876 InRadar P2 Normal --- 1 kkinnunen kkinnunen dino kbr kkinnunen webkit-bug-importer oldest_to_newest 1959521 0 kkinnunen 2023-06-02 04:36:06 -0700 GPUP WebGL flush() and finish() are asynchronous Should be synchronous 1959522 1 webkit-bug-importer 2023-06-02 04:38:12 -0700 <rdar://problem/110163403> 1959523 2 kkinnunen 2023-06-02 04:39:45 -0700 Pull request: https://github.com/WebKit/WebKit/pull/14623 1959525 3 kkinnunen 2023-06-02 04:42:35 -0700 Blocks bug 252876 for benchmarking before/after read pixels perf 1959558 4 kbr 2023-06-02 09:48:05 -0700 The side-effects of flush() and finish() can't be observed by application code in the WebGL context. Even with finish(), there's a WebGL spec difference compared to OpenGL ES that the status of objects like queries can't change unless control is returned to the browser. For this reason it should be safe to leave these asynchronous, and I think WebKit might incur a performance penalty compared to other implementations by making them synchronous. If it's necessary to use these for synchronization with other subsystems in WebKit like the media stack, I'd suggest adding another internal primitive that can't be called by the web platform - Chromium does this. 1959560 5 kkinnunen 2023-06-02 09:51:06 -0700 Think Chrome's implementation is also synchronous, e.g. the call between renderer and GPU process. I think previously we discussed wrt "real finish vs gl.finish as gl.flush()", which cannot be observed. 1959562 6 kkinnunen 2023-06-02 09:52:20 -0700 Or, maybe not maybe it is indeed async? 1959565 7 kbr 2023-06-02 09:57:32 -0700 In Chrome at the lowest level, Finish is synchronous: https://source.chromium.org/chromium/chromium/src/+/refs/heads/main:gpu/command_buffer/client/cmd_buffer_helper.cc;l=220;drc=b8a0323a84f483b25e94b3a24d80fda16c5dd1ae;bpv=1;bpt=1 but Flush isn't: https://source.chromium.org/chromium/chromium/src/+/refs/heads/main:gpu/command_buffer/client/cmd_buffer_helper.cc;l=173;drc=b8a0323a84f483b25e94b3a24d80fda16c5dd1ae;bpv=0;bpt=1 However, the WebGL implementation never calls the underlying Finish, only Flush: https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/renderer/modules/webgl/webgl_rendering_context_base.cc;l=3034?q=webgl_rendering_context_base.cc 1959850 8 kkinnunen 2023-06-05 04:18:19 -0700 > However, the WebGL implementation never calls the underlying Finish, only Flush: Ah, right! I keep on forgetting.