Reduce gratuitous resets for OneShotTimer
OneShotTimer::reset just resets an internal timer thread for it to go
back to sleep. When just implemented with semaphores, this introduces a
lot of syscall churn due to posting a semaphore -> waking up the timer
thread -> having the thread go back to sleep. Instead, we can avoid
resetting the timer if we know that the thread is about to wait for a
short amount of time, and only reset the timer if the thread is in an
idle state.
This patch reduces instruction counts by 5%, and CPU cycles incurred by
an additional 5%.
Bug: 232272570
Test: bouncy ball
Change-Id: I83f968042395857237875aab8dca0e6b90d392cb
diff --git a/services/surfaceflinger/Scheduler/OneShotTimer.h b/services/surfaceflinger/Scheduler/OneShotTimer.h
index 09265bb..2017c31 100644
--- a/services/surfaceflinger/Scheduler/OneShotTimer.h
+++ b/services/surfaceflinger/Scheduler/OneShotTimer.h
@@ -103,6 +103,8 @@
// check in the main loop if they were.
std::atomic<bool> mResetTriggered = false;
std::atomic<bool> mStopTriggered = false;
+ std::atomic<bool> mWaiting = false;
+ std::atomic<std::chrono::steady_clock::time_point> mLastResetTime;
};
} // namespace scheduler