[SurfaceFlinger] Exclude first vsync duration from period calculation
Some displays don't exit from idle state immediately when vsync is
enabled through the kernel idle timer, so exclude the first vsync period
instead of just the first sample.
Bug: 136197211
Test: Scrolling through settings
Change-Id: I899fec289c8b08cfaa3264f7f6291a6fac489ab8
diff --git a/services/surfaceflinger/Scheduler/DispSync.cpp b/services/surfaceflinger/Scheduler/DispSync.cpp
index 83fd42b..0c94052 100644
--- a/services/surfaceflinger/Scheduler/DispSync.cpp
+++ b/services/surfaceflinger/Scheduler/DispSync.cpp
@@ -668,7 +668,13 @@
nsecs_t durationSum = 0;
nsecs_t minDuration = INT64_MAX;
nsecs_t maxDuration = 0;
- for (size_t i = 1; i < mNumResyncSamples; i++) {
+ // We skip the first 2 samples because the first vsync duration on some
+ // devices may be much more inaccurate than on other devices, e.g. due
+ // to delays in ramping up from a power collapse. By doing so this
+ // actually increases the accuracy of the DispSync model even though
+ // we're effectively relying on fewer sample points.
+ static constexpr size_t numSamplesSkipped = 2;
+ for (size_t i = numSamplesSkipped; i < mNumResyncSamples; i++) {
size_t idx = (mFirstResyncSample + i) % MAX_RESYNC_SAMPLES;
size_t prev = (idx + MAX_RESYNC_SAMPLES - 1) % MAX_RESYNC_SAMPLES;
nsecs_t duration = mResyncSamples[idx] - mResyncSamples[prev];
@@ -679,15 +685,14 @@
// Exclude the min and max from the average
durationSum -= minDuration + maxDuration;
- mPeriod = durationSum / (mNumResyncSamples - 3);
+ mPeriod = durationSum / (mNumResyncSamples - numSamplesSkipped - 2);
ALOGV("[%s] mPeriod = %" PRId64, mName, ns2us(mPeriod));
double sampleAvgX = 0;
double sampleAvgY = 0;
double scale = 2.0 * M_PI / double(mPeriod);
- // Intentionally skip the first sample
- for (size_t i = 1; i < mNumResyncSamples; i++) {
+ for (size_t i = numSamplesSkipped; i < mNumResyncSamples; i++) {
size_t idx = (mFirstResyncSample + i) % MAX_RESYNC_SAMPLES;
nsecs_t sample = mResyncSamples[idx] - mReferenceTime;
double samplePhase = double(sample % mPeriod) * scale;
@@ -695,8 +700,8 @@
sampleAvgY += sin(samplePhase);
}
- sampleAvgX /= double(mNumResyncSamples - 1);
- sampleAvgY /= double(mNumResyncSamples - 1);
+ sampleAvgX /= double(mNumResyncSamples - numSamplesSkipped);
+ sampleAvgY /= double(mNumResyncSamples - numSamplesSkipped);
mPhase = nsecs_t(atan2(sampleAvgY, sampleAvgX) / scale);
