[fuchsia] change kMaxFramesInFlight to 3, add offset option #16425
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| fml::TimePoint next_vsync = SnapToNextPhase(now, last_presentation_time, | ||
| vsync_info.presentation_interval); | ||
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| auto vsync_start_time = next_vsync - vsync_offset; |
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Nit: next_vsync_start_time might make more sense here.
| // outstanding at any time. This is equivalent to how many times it has | ||
| // called Present2() before receiving an OnFramePresented() event. | ||
| static constexpr int kMaxFramesInFlight = 2; | ||
| static constexpr int kMaxFramesInFlight = 3; |
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I am not sure about the nature of scheduling flexibility offered by this change. But, in the past, we have found that increasing the pipeline depth has adverse effects when it comes to render frames with inconsistent rasterizer times.
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It's important to note that this doesn't actually impact the Flutter pipeline as you normally think of it, but rather how Flutter Present()s content to Scenic.
Right now Flutter only has two frames in flight, which means that if we are effectively "double buffered." If we then miss frame A Flutter can't submit frame C, because B is also in flight. By changing this to 3, we can miss frame A and still have frames B and C in flight too, ensuring that one frame miss won't result in another one.
If we were targeting <=16ms Scenic+Flutter frame build times then this wouldn't matter. But by increasing how many frames in flight we can have we can target 32ms frame build times and not suffer a double penalty for missing a frame.
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It's important to note that this doesn't actually impact the Flutter pipeline as you normally think of it, but rather how Flutter Present()s content to Scenic.
I realize that. Just wanted to know the reasoning behind this change. Thanks for the clarifications.
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To give more flexibiltiy in scheduling, we change the number of frames in flight we can have at one time to 3. We also introduce an offset from VSync that Flutter can use to begin its work at. It is currently set at 0ms, signalling no change from previous behavior.
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* d5442b8 Roll src/third_party/skia bc3307c395e2..ebc00f97fab1 (21 commits) (flutter/engine#16429) * 76b291a Added a plugin method that gets called when the engine is about to be deleted (flutter/engine#16336) * 07f25c5 fix bad reference to maxDiffRatePercent (flutter/engine#16440) * 41d50c2 Reland #16206: "[web] Correct getPositionForOffset for multi-line paragraphs" (flutter/engine#16365) * f25d325 [fuchsia] change kMaxFramesInFlight to 3 (flutter/engine#16425) * 473f559 Suppress some deprecation warnings on Windows (flutter/engine#16416) * 2e34ad6 Roll fuchsia/sdk/core/mac-amd64 from ubThi... to fvWgE... (flutter/engine#16454) * 47c02e6 Roll src/third_party/skia ebc00f97fab1..cbf79b95c2d4 (4 commits) (flutter/engine#16456) * 3d1b112 Roll buildroot (flutter/engine#16419) * 28e6637 Add explicit casts to printing of function pointers (flutter/engine#16370) * 9ad81da Wrap strdup to use compliant name on Windows (flutter/engine#16372) * 9708e52 Roll rapidjson (flutter/engine#16347) * f06ebba Include <memory> in hb_wrapper.h because unique_ptr is used. (flutter/engine#16442) * e530376 Roll fuchsia/sdk/core/linux-amd64 from VJv0H... to A9STP... (flutter/engine#16457) * 4cc41ae Roll src/third_party/skia cbf79b95c2d4..4721e067812f (1 commits) (flutter/engine#16459) * 2f233ed Roll src/third_party/skia 4721e067812f..f6e3eaf05150 (1 commits) (flutter/engine#16461) * b0b0ed8 Roll src/third_party/skia f6e3eaf05150..cc21d0c1f2ce (1 commits) (flutter/engine#16463) * 7fea936 Roll src/third_party/skia cc21d0c1f2ce..116b33e8ab21 (3 commits) (flutter/engine#16466) * 001b3a0 Roll src/third_party/skia 116b33e8ab21..7f36405ea3ec (3 commits) (flutter/engine#16471) * f3ce90e Reset width/height before deallocation for Safari allocation bug. (flutter/engine#16469)
To give more flexibility in scheduling, we change the number of frames in flight we can have at one time to 3. We also introduce an offset from VSync that Flutter can use to begin its work at. It is currently set at 0ms, matching previous behavior.
This reverts commit 6ff3ecc.
To give more flexibiltiy in scheduling, we change the number of frames
in flight we can have at one time to 3. We also introduce an offset from
VSync that Flutter can use to begin its work at. It is currently set at
0ms, signalling no change from previous behavior.