SF: VSyncDispatch: correct vsync prediction drift
Refine VSyncDispatch::schedule implementation so that refining
the prediction by small amounts would not lead to skipped callbacks.
The current implementation did not account for a case where
a valid vsync callback would be skipped. (exposed
in unit testing). Like the rest of VSyncDispatch, this
code is flagged off (ie, latent, not production code yet)
Fixes: 145213786
Bug: 146050690
Test: 6 new unit tests, 3 unit test change
Test: validation via systrace
Change-Id: I400fc5e3c181b49ab237b0dd0da2a62e38522fa0
diff --git a/services/surfaceflinger/Scheduler/VSyncDispatch.h b/services/surfaceflinger/Scheduler/VSyncDispatch.h
index e001080..56b3252 100644
--- a/services/surfaceflinger/Scheduler/VSyncDispatch.h
+++ b/services/surfaceflinger/Scheduler/VSyncDispatch.h
@@ -26,7 +26,7 @@
class TimeKeeper;
class VSyncTracker;
-enum class ScheduleResult { Scheduled, ReScheduled, CannotSchedule, Error };
+enum class ScheduleResult { Scheduled, CannotSchedule, Error };
enum class CancelResult { Cancelled, TooLate, Error };
/*
@@ -83,7 +83,6 @@
* \param [in] earliestVsync The targeted display time. This will be snapped to the closest
* predicted vsync time after earliestVsync.
* \return A ScheduleResult::Scheduled if callback was scheduled.
- * A ScheduleResult::ReScheduled if callback was rescheduled.
* A ScheduleResult::CannotSchedule
* if (workDuration - earliestVsync) is in the past, or
* if a callback was dispatched for the predictedVsync already.
diff --git a/services/surfaceflinger/Scheduler/VSyncDispatchTimerQueue.cpp b/services/surfaceflinger/Scheduler/VSyncDispatchTimerQueue.cpp
index a79fe98..48f2abb 100644
--- a/services/surfaceflinger/Scheduler/VSyncDispatchTimerQueue.cpp
+++ b/services/surfaceflinger/Scheduler/VSyncDispatchTimerQueue.cpp
@@ -29,8 +29,13 @@
TimeKeeper::~TimeKeeper() = default;
VSyncDispatchTimerQueueEntry::VSyncDispatchTimerQueueEntry(std::string const& name,
- std::function<void(nsecs_t)> const& cb)
- : mName(name), mCallback(cb), mWorkDuration(0), mEarliestVsync(0) {}
+ std::function<void(nsecs_t)> const& cb,
+ nsecs_t minVsyncDistance)
+ : mName(name),
+ mCallback(cb),
+ mWorkDuration(0),
+ mEarliestVsync(0),
+ mMinVsyncDistance(minVsyncDistance) {}
std::optional<nsecs_t> VSyncDispatchTimerQueueEntry::lastExecutedVsyncTarget() const {
return mLastDispatchTime;
@@ -49,18 +54,28 @@
ScheduleResult VSyncDispatchTimerQueueEntry::schedule(nsecs_t workDuration, nsecs_t earliestVsync,
VSyncTracker& tracker, nsecs_t now) {
- auto const nextVsyncTime =
+ auto nextVsyncTime =
tracker.nextAnticipatedVSyncTimeFrom(std::max(earliestVsync, now + workDuration));
- if (mLastDispatchTime >= nextVsyncTime) { // already dispatched a callback for this vsync
- return ScheduleResult::CannotSchedule;
+
+ bool const wouldSkipAVsyncTarget =
+ mArmedInfo && (nextVsyncTime > (mArmedInfo->mActualVsyncTime + mMinVsyncDistance));
+ if (wouldSkipAVsyncTarget) {
+ return ScheduleResult::Scheduled;
+ }
+
+ bool const alreadyDispatchedForVsync = mLastDispatchTime &&
+ ((*mLastDispatchTime + mMinVsyncDistance) >= nextVsyncTime &&
+ (*mLastDispatchTime - mMinVsyncDistance) <= nextVsyncTime);
+ if (alreadyDispatchedForVsync) {
+ nextVsyncTime =
+ tracker.nextAnticipatedVSyncTimeFrom(*mLastDispatchTime + mMinVsyncDistance);
}
auto const nextWakeupTime = nextVsyncTime - workDuration;
- auto result = mArmedInfo ? ScheduleResult::ReScheduled : ScheduleResult::Scheduled;
mWorkDuration = workDuration;
mEarliestVsync = earliestVsync;
mArmedInfo = {nextWakeupTime, nextVsyncTime};
- return result;
+ return ScheduleResult::Scheduled;
}
void VSyncDispatchTimerQueueEntry::update(VSyncTracker& tracker, nsecs_t now) {
@@ -101,8 +116,12 @@
}
VSyncDispatchTimerQueue::VSyncDispatchTimerQueue(std::unique_ptr<TimeKeeper> tk,
- VSyncTracker& tracker, nsecs_t timerSlack)
- : mTimeKeeper(std::move(tk)), mTracker(tracker), mTimerSlack(timerSlack) {}
+ VSyncTracker& tracker, nsecs_t timerSlack,
+ nsecs_t minVsyncDistance)
+ : mTimeKeeper(std::move(tk)),
+ mTracker(tracker),
+ mTimerSlack(timerSlack),
+ mMinVsyncDistance(minVsyncDistance) {}
VSyncDispatchTimerQueue::~VSyncDispatchTimerQueue() {
std::lock_guard<decltype(mMutex)> lk(mMutex);
@@ -187,7 +206,8 @@
mCallbacks
.emplace(++mCallbackToken,
std::make_shared<VSyncDispatchTimerQueueEntry>(callbackName,
- callbackFn))
+ callbackFn,
+ mMinVsyncDistance))
.first->first};
}
@@ -277,12 +297,16 @@
}
ScheduleResult VSyncCallbackRegistration::schedule(nsecs_t workDuration, nsecs_t earliestVsync) {
- if (!mValidToken) return ScheduleResult::Error;
+ if (!mValidToken) {
+ return ScheduleResult::Error;
+ }
return mDispatch.get().schedule(mToken, workDuration, earliestVsync);
}
CancelResult VSyncCallbackRegistration::cancel() {
- if (!mValidToken) return CancelResult::Error;
+ if (!mValidToken) {
+ return CancelResult::Error;
+ }
return mDispatch.get().cancel(mToken);
}
diff --git a/services/surfaceflinger/Scheduler/VSyncDispatchTimerQueue.h b/services/surfaceflinger/Scheduler/VSyncDispatchTimerQueue.h
index fc78da3..0c9b4fe 100644
--- a/services/surfaceflinger/Scheduler/VSyncDispatchTimerQueue.h
+++ b/services/surfaceflinger/Scheduler/VSyncDispatchTimerQueue.h
@@ -36,7 +36,8 @@
// Valid transition: disarmed -> armed ( when scheduled )
// Valid transition: armed -> running -> disarmed ( when timer is called)
// Valid transition: armed -> disarmed ( when cancelled )
- VSyncDispatchTimerQueueEntry(std::string const& name, std::function<void(nsecs_t)> const& fn);
+ VSyncDispatchTimerQueueEntry(std::string const& name, std::function<void(nsecs_t)> const& fn,
+ nsecs_t minVsyncDistance);
std::string_view name() const;
// Start: functions that are not threadsafe.
@@ -72,6 +73,7 @@
nsecs_t mWorkDuration;
nsecs_t mEarliestVsync;
+ nsecs_t const mMinVsyncDistance;
struct ArmingInfo {
nsecs_t mActualWakeupTime;
@@ -91,8 +93,15 @@
*/
class VSyncDispatchTimerQueue : public VSyncDispatch {
public:
+ // Constructs a VSyncDispatchTimerQueue.
+ // \param[in] tk A timekeeper.
+ // \param[in] tracker A tracker.
+ // \param[in] timerSlack The threshold at which different similarly timed callbacks
+ // should be grouped into one wakeup.
+ // \param[in] minVsyncDistance The minimum distance between two vsync estimates before the
+ // vsyncs are considered the same vsync event.
explicit VSyncDispatchTimerQueue(std::unique_ptr<TimeKeeper> tk, VSyncTracker& tracker,
- nsecs_t timerSlack);
+ nsecs_t timerSlack, nsecs_t minVsyncDistance);
~VSyncDispatchTimerQueue();
CallbackToken registerCallback(std::function<void(nsecs_t)> const& callbackFn,
@@ -119,6 +128,7 @@
std::unique_ptr<TimeKeeper> const mTimeKeeper;
VSyncTracker& mTracker;
nsecs_t const mTimerSlack;
+ nsecs_t const mMinVsyncDistance;
std::mutex mutable mMutex;
size_t mCallbackToken GUARDED_BY(mMutex) = 0;
diff --git a/services/surfaceflinger/Scheduler/VSyncReactor.cpp b/services/surfaceflinger/Scheduler/VSyncReactor.cpp
index 49ab6c1..47e3f4f 100644
--- a/services/surfaceflinger/Scheduler/VSyncReactor.cpp
+++ b/services/surfaceflinger/Scheduler/VSyncReactor.cpp
@@ -14,6 +14,8 @@
* limitations under the License.
*/
+#undef LOG_TAG
+#define LOG_TAG "VSyncReactor"
//#define LOG_NDEBUG 0
#include "VSyncReactor.h"
#include <log/log.h>
@@ -59,8 +61,9 @@
mStopped = false;
mOffset = offset;
- // TODO: (b/145213786) check the return code here sensibly
- mRegistration.schedule(calculateWorkload(), mLastCallTime);
+ auto const schedule_result = mRegistration.schedule(calculateWorkload(), mLastCallTime);
+ LOG_ALWAYS_FATAL_IF((schedule_result != ScheduleResult::Scheduled),
+ "Error scheduling callback: rc %X", schedule_result);
}
void setPeriod(nsecs_t period) {
@@ -91,7 +94,9 @@
{
std::lock_guard<std::mutex> lk(mMutex);
- mRegistration.schedule(calculateWorkload(), vsynctime);
+ auto const schedule_result = mRegistration.schedule(calculateWorkload(), vsynctime);
+ LOG_ALWAYS_FATAL_IF((schedule_result != ScheduleResult::Scheduled),
+ "Error rescheduling callback: rc %X", schedule_result);
}
}