Commit e67937fe authored Feb 06, 2025 by Su Hong Koo

SF: Feed presentation fences to external displays' vsync predictors

Currently, the presentation fences from hardware composer are only fed to vsync
predictors for internal displays. Since presentation fence signal times are
used to keep the prediction model fresh, external displays without fence
timings become significantly less accurate after some time (seconds).

The drift in the external displays’ vsync prediction results in inaccurate
expectation presentation times being fed across SurfaceFlinger, and may result
in inaccurate metrics/traces.

This CL changes the qualification for feeding presentation fences to vsync
schedules from is internal to is physical display, which is implicit.

Refer to the bug for traces and more detail.

Flag: EXEMPT bugfix
Bug: 394879543
Test: manual testing and verification using frame timeline/tracing
Change-Id: I69321c6eb0682adb5763c7281d376055d59de8fd

parent ff045163

services/surfaceflinger/SurfaceFlinger.cpp

+1 −7

Original line number	Diff line number	Diff line
		@@ -3459,14 +3459,8 @@ void SurfaceFlinger::onCompositionPresented(PhysicalDisplayId pacesetterId,
		mTimeStats->setPresentFenceGlobal(pacesetterPresentFenceTime);

		for (auto&& [id, presentFence] : presentFences) {
		ftl::FakeGuard guard(mStateLock);
		const bool isInternalDisplay =
		mPhysicalDisplays.get(id).transform(&PhysicalDisplay::isInternal).value_or(false);

		if (isInternalDisplay) {
		mScheduler->addPresentFence(id, std::move(presentFence));
		}
		}

		const bool hasPacesetterDisplay =
		pacesetterDisplay && getHwComposer().isConnected(pacesetterId);