Merge "SF: VSyncPredictor correct calculation" (b35b6c42) · Commits · e / os / android_frameworks_native

services/surfaceflinger/Scheduler/Timer.cpp

+1 −1

Original line number	Diff line number	Diff line
		@@ -85,7 +85,7 @@ void Timer::alarmIn(std::function<void()> const& cb, nsecs_t fireIn) {
		};

		if (timerfd_settime(mTimerFd, 0, &new_timer, &old_timer)) {
		ALOGW("Failed to set timerfd");
		ALOGW("Failed to set timerfd %s (%i)", strerror(errno), errno);
		}
		}

+17 −4

Original line number	Diff line number	Diff line
		@@ -23,6 +23,7 @@
		#include <utils/Trace.h>
		#include <algorithm>
		#include <chrono>
		#include <sstream>
		#include "SchedulerUtils.h"

		namespace android::scheduler {
		@@ -153,12 +154,24 @@ nsecs_t VSyncPredictor::nextAnticipatedVSyncTimeFrom(nsecs_t timePoint) const {
		}

		auto const oldest = *std::min_element(timestamps.begin(), timestamps.end());
		auto const ordinalRequest = (timePoint - oldest + slope) / slope;

		// See b/145667109, the ordinal calculation must take into account the intercept.
		auto const zeroPoint = oldest + intercept;
		auto const ordinalRequest = (timePoint - zeroPoint + slope) / slope;
		auto const prediction = (ordinalRequest * slope) + intercept + oldest;

		ALOGV("prediction made from: %" PRId64 " prediction: %" PRId64 " (+%" PRId64 ") slope: %" PRId64
		" intercept: %" PRId64,
		timePoint, prediction, prediction - timePoint, slope, intercept);
		auto const printer = [&, slope = slope, intercept = intercept] {
		std::stringstream str;
		str << "prediction made from: " << timePoint << "prediction: " << prediction << " (+"
		<< prediction - timePoint << ") slope: " << slope << " intercept: " << intercept
		<< "oldestTS: " << oldest << " ordinal: " << ordinalRequest;
		return str.str();
		};

		ALOGV("%s", printer().c_str());
		LOG_ALWAYS_FATAL_IF(prediction < timePoint, "VSyncPredictor: model miscalculation: %s",
		printer().c_str());

		return prediction;
		}

+32 −0

Original line number	Diff line number	Diff line
		@@ -319,4 +319,36 @@ TEST_F(VSyncPredictorTest, idealModelPredictionsBeforeRegressionModelIsBuilt) {
		}
		}

		// See b/145667109, and comment in prod code under test.
		TEST_F(VSyncPredictorTest, doesNotPredictBeforeTimePointWithHigherIntercept) {
		std::vector<nsecs_t> const simulatedVsyncs{
		158929578733000,
		158929306806205, // oldest TS in ringbuffer
		158929650879052,
		158929661969209,
		158929684198847,
		158929695268171,
		158929706370359,
		};
		auto const idealPeriod = 11111111;
		auto const expectedPeriod = 11113500;
		auto const expectedIntercept = -395335;

		tracker.setPeriod(idealPeriod);
		for (auto const& timestamp : simulatedVsyncs) {
		tracker.addVsyncTimestamp(timestamp);
		}

		auto [slope, intercept] = tracker.getVSyncPredictionModel();
		EXPECT_THAT(slope, IsCloseTo(expectedPeriod, mMaxRoundingError));
		EXPECT_THAT(intercept, IsCloseTo(expectedIntercept, mMaxRoundingError));

		// (timePoint - oldestTS) % expectedPeriod works out to be: 395334
		// (timePoint - oldestTS) / expectedPeriod works out to be: 38.96
		// so failure to account for the offset will floor the ordinal to 38, which was in the past.
		auto const timePoint = 158929728723871;
		auto const prediction = tracker.nextAnticipatedVSyncTimeFrom(timePoint);
		EXPECT_THAT(prediction, Ge(timePoint));
		}

		} // namespace android::scheduler