SF: add VSyncPredictor implementation
Adds an implementation of VSyncPredictor, an object that will
predict vsync events for multiple fixed-rate vsync systems.
The prediction is based on both the HWVsync signal and the
presentation fence timings for the VSyncDispatch object.
Bug: 140201379
Fixes: 140302888
Test: 13 new unit tests
Change-Id: I195902cc70561d028741d822e4001ad21ab391cf
diff --git a/services/surfaceflinger/tests/unittests/Android.bp b/services/surfaceflinger/tests/unittests/Android.bp
index c6c3d29..0c4a752 100644
--- a/services/surfaceflinger/tests/unittests/Android.bp
+++ b/services/surfaceflinger/tests/unittests/Android.bp
@@ -56,6 +56,7 @@
"StrongTypingTest.cpp",
"VSyncDispatchTimerQueueTest.cpp",
"VSyncDispatchRealtimeTest.cpp",
+ "VSyncPredictorTest.cpp",
"mock/DisplayHardware/MockComposer.cpp",
"mock/DisplayHardware/MockDisplay.cpp",
"mock/DisplayHardware/MockPowerAdvisor.cpp",
diff --git a/services/surfaceflinger/tests/unittests/VSyncPredictorTest.cpp b/services/surfaceflinger/tests/unittests/VSyncPredictorTest.cpp
new file mode 100644
index 0000000..d0c8090
--- /dev/null
+++ b/services/surfaceflinger/tests/unittests/VSyncPredictorTest.cpp
@@ -0,0 +1,322 @@
+/*
+ * Copyright 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#undef LOG_TAG
+#define LOG_TAG "LibSurfaceFlingerUnittests"
+#define LOG_NDEBUG 0
+
+#include "Scheduler/VSyncPredictor.h"
+
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+#include <algorithm>
+#include <chrono>
+#include <utility>
+
+using namespace testing;
+using namespace std::literals;
+
+namespace android::scheduler {
+
+MATCHER_P2(IsCloseTo, value, tolerance, "is within tolerance") {
+ return arg <= value + tolerance && value >= value - tolerance;
+}
+
+std::vector<nsecs_t> generateVsyncTimestamps(size_t count, nsecs_t period, nsecs_t bias) {
+ std::vector<nsecs_t> vsyncs(count);
+ std::generate(vsyncs.begin(), vsyncs.end(),
+ [&, n = 0]() mutable { return n++ * period + bias; });
+ return vsyncs;
+}
+
+struct VSyncPredictorTest : testing::Test {
+ nsecs_t mNow = 0;
+ nsecs_t mPeriod = 1000;
+ static constexpr size_t kHistorySize = 10;
+ static constexpr size_t kMinimumSamplesForPrediction = 6;
+ static constexpr size_t kOutlierTolerancePercent = 25;
+ static constexpr nsecs_t mMaxRoundingError = 100;
+
+ VSyncPredictor tracker{mPeriod, kHistorySize, kMinimumSamplesForPrediction,
+ kOutlierTolerancePercent};
+};
+
+TEST_F(VSyncPredictorTest, reportsAnticipatedPeriod) {
+ auto [slope, intercept] = tracker.getVSyncPredictionModel();
+
+ EXPECT_THAT(slope, Eq(mPeriod));
+ EXPECT_THAT(intercept, Eq(0));
+
+ auto const changedPeriod = 2000;
+ tracker.setPeriod(changedPeriod);
+ std::tie(slope, intercept) = tracker.getVSyncPredictionModel();
+ EXPECT_THAT(slope, Eq(changedPeriod));
+ EXPECT_THAT(intercept, Eq(0));
+}
+
+TEST_F(VSyncPredictorTest, reportsSamplesNeededWhenHasNoDataPoints) {
+ for (auto i = 0u; i < kMinimumSamplesForPrediction; i++) {
+ EXPECT_TRUE(tracker.needsMoreSamples(mNow += mPeriod));
+ tracker.addVsyncTimestamp(mNow);
+ }
+ EXPECT_FALSE(tracker.needsMoreSamples(mNow));
+}
+
+TEST_F(VSyncPredictorTest, reportsSamplesNeededAfterExplicitRateChange) {
+ for (auto i = 0u; i < kMinimumSamplesForPrediction; i++) {
+ tracker.addVsyncTimestamp(mNow += mPeriod);
+ }
+ EXPECT_FALSE(tracker.needsMoreSamples(mNow));
+
+ auto const changedPeriod = mPeriod * 2;
+ tracker.setPeriod(changedPeriod);
+ EXPECT_TRUE(tracker.needsMoreSamples(mNow));
+
+ for (auto i = 0u; i < kMinimumSamplesForPrediction; i++) {
+ EXPECT_TRUE(tracker.needsMoreSamples(mNow += changedPeriod));
+ tracker.addVsyncTimestamp(mNow);
+ }
+ EXPECT_FALSE(tracker.needsMoreSamples(mNow));
+}
+
+TEST_F(VSyncPredictorTest, transitionsToModelledPointsAfterSynthetic) {
+ auto last = mNow;
+ auto const bias = 10;
+ for (auto i = 0u; i < kMinimumSamplesForPrediction; i++) {
+ EXPECT_THAT(tracker.nextAnticipatedVSyncTimeFrom(mNow), Eq(last + mPeriod));
+ mNow += mPeriod - bias;
+ last = mNow;
+ tracker.addVsyncTimestamp(mNow);
+ mNow += bias;
+ }
+
+ EXPECT_THAT(tracker.nextAnticipatedVSyncTimeFrom(mNow), Eq(mNow + mPeriod - bias));
+ EXPECT_THAT(tracker.nextAnticipatedVSyncTimeFrom(mNow + 100), Eq(mNow + mPeriod - bias));
+ EXPECT_THAT(tracker.nextAnticipatedVSyncTimeFrom(mNow + 990), Eq(mNow + 2 * mPeriod - bias));
+}
+
+TEST_F(VSyncPredictorTest, uponNotifiedOfInaccuracyUsesSynthetic) {
+ auto const slightlyLessPeriod = mPeriod - 10;
+ auto const changedPeriod = mPeriod - 1;
+ for (auto i = 0u; i < kMinimumSamplesForPrediction; i++) {
+ tracker.addVsyncTimestamp(mNow += slightlyLessPeriod);
+ }
+
+ EXPECT_THAT(tracker.nextAnticipatedVSyncTimeFrom(mNow), Eq(mNow + slightlyLessPeriod));
+ tracker.setPeriod(changedPeriod);
+ EXPECT_THAT(tracker.nextAnticipatedVSyncTimeFrom(mNow), Eq(mNow + changedPeriod));
+}
+
+TEST_F(VSyncPredictorTest, adaptsToFenceTimelines_60hzHighVariance) {
+ // these are precomputed simulated 16.6s vsyncs with uniform distribution +/- 1.6ms error
+ std::vector<nsecs_t> const simulatedVsyncs{
+ 15492949, 32325658, 49534984, 67496129, 84652891,
+ 100332564, 117737004, 132125931, 149291099, 165199602,
+ };
+ auto constexpr idealPeriod = 16600000;
+ auto constexpr expectedPeriod = 16639242;
+ auto constexpr expectedIntercept = 1049341;
+
+ 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));
+}
+
+TEST_F(VSyncPredictorTest, adaptsToFenceTimelines_90hzLowVariance) {
+ // these are precomputed simulated 11.1 vsyncs with uniform distribution +/- 1ms error
+ std::vector<nsecs_t> const simulatedVsyncs{
+ 11167047, 22603464, 32538479, 44938134, 56321268,
+ 66730346, 78062637, 88171429, 99707843, 111397621,
+ };
+ auto idealPeriod = 11110000;
+ auto expectedPeriod = 11089413;
+ auto expectedIntercept = 94421;
+
+ 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));
+}
+
+TEST_F(VSyncPredictorTest, adaptsToFenceTimelinesDiscontinuous_22hzLowVariance) {
+ // these are 11.1s vsyncs with low variance, randomly computed, between -1 and 1ms
+ std::vector<nsecs_t> const simulatedVsyncs{
+ 45259463, // 0
+ 91511026, // 1
+ 136307650, // 2
+ 1864501714, // 40
+ 1908641034, // 41
+ 1955278544, // 42
+ 4590180096, // 100
+ 4681594994, // 102
+ 5499224734, // 120
+ 5591378272, // 122
+ };
+ auto idealPeriod = 45454545;
+ auto expectedPeriod = 45450152;
+ auto expectedIntercept = 469647;
+
+ 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));
+}
+
+TEST_F(VSyncPredictorTest, againstOutliersDiscontinuous_500hzLowVariance) {
+ std::vector<nsecs_t> const simulatedVsyncs{
+ 1992548, // 0
+ 4078038, // 1
+ 6165794, // 2
+ 7958171, // 3
+ 10193537, // 4
+ 2401840200, // 1200
+ 2403000000, // an outlier that should be excluded (1201 and a half)
+ 2405803629, // 1202
+ 2408028599, // 1203
+ 2410121051, // 1204
+ };
+ auto idealPeriod = 2000000;
+ auto expectedPeriod = 1999892;
+ auto expectedIntercept = 175409;
+
+ 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));
+}
+
+TEST_F(VSyncPredictorTest, handlesVsyncChange) {
+ auto const fastPeriod = 100;
+ auto const fastTimeBase = 100;
+ auto const slowPeriod = 400;
+ auto const slowTimeBase = 800;
+ auto const simulatedVsyncsFast =
+ generateVsyncTimestamps(kMinimumSamplesForPrediction, fastPeriod, fastTimeBase);
+ auto const simulatedVsyncsSlow =
+ generateVsyncTimestamps(kMinimumSamplesForPrediction, slowPeriod, slowTimeBase);
+
+ tracker.setPeriod(fastPeriod);
+ for (auto const& timestamp : simulatedVsyncsFast) {
+ tracker.addVsyncTimestamp(timestamp);
+ }
+
+ auto const mMaxRoundingError = 100;
+ auto [slope, intercept] = tracker.getVSyncPredictionModel();
+ EXPECT_THAT(slope, IsCloseTo(fastPeriod, mMaxRoundingError));
+ EXPECT_THAT(intercept, IsCloseTo(0, mMaxRoundingError));
+
+ tracker.setPeriod(slowPeriod);
+ for (auto const& timestamp : simulatedVsyncsSlow) {
+ tracker.addVsyncTimestamp(timestamp);
+ }
+ std::tie(slope, intercept) = tracker.getVSyncPredictionModel();
+ EXPECT_THAT(slope, IsCloseTo(slowPeriod, mMaxRoundingError));
+ EXPECT_THAT(intercept, IsCloseTo(0, mMaxRoundingError));
+}
+
+TEST_F(VSyncPredictorTest, willBeAccurateUsingPriorResultsForRate) {
+ auto const fastPeriod = 101000;
+ auto const fastTimeBase = fastPeriod - 500;
+ auto const fastPeriod2 = 99000;
+
+ auto const slowPeriod = 400000;
+ auto const slowTimeBase = 800000 - 201;
+ auto const simulatedVsyncsFast =
+ generateVsyncTimestamps(kMinimumSamplesForPrediction, fastPeriod, fastTimeBase);
+ auto const simulatedVsyncsSlow =
+ generateVsyncTimestamps(kMinimumSamplesForPrediction, slowPeriod, slowTimeBase);
+ auto const simulatedVsyncsFast2 =
+ generateVsyncTimestamps(kMinimumSamplesForPrediction, fastPeriod2, fastTimeBase);
+
+ auto idealPeriod = 100000;
+ tracker.setPeriod(idealPeriod);
+ for (auto const& timestamp : simulatedVsyncsFast) {
+ tracker.addVsyncTimestamp(timestamp);
+ }
+ auto [slope, intercept] = tracker.getVSyncPredictionModel();
+ EXPECT_THAT(slope, Eq(fastPeriod));
+ EXPECT_THAT(intercept, Eq(0));
+
+ tracker.setPeriod(slowPeriod);
+ for (auto const& timestamp : simulatedVsyncsSlow) {
+ tracker.addVsyncTimestamp(timestamp);
+ }
+
+ // we had a model for 100ns mPeriod before, use that until the new samples are
+ // sufficiently built up
+ tracker.setPeriod(idealPeriod);
+ std::tie(slope, intercept) = tracker.getVSyncPredictionModel();
+ EXPECT_THAT(slope, Eq(fastPeriod));
+ EXPECT_THAT(intercept, Eq(0));
+
+ for (auto const& timestamp : simulatedVsyncsFast2) {
+ tracker.addVsyncTimestamp(timestamp);
+ }
+ std::tie(slope, intercept) = tracker.getVSyncPredictionModel();
+ EXPECT_THAT(slope, Eq(fastPeriod2));
+ EXPECT_THAT(intercept, Eq(0));
+}
+
+TEST_F(VSyncPredictorTest, willBecomeInaccurateAfterA_longTimeWithNoSamples) {
+ auto const simulatedVsyncs = generateVsyncTimestamps(kMinimumSamplesForPrediction, mPeriod, 0);
+
+ for (auto const& timestamp : simulatedVsyncs) {
+ tracker.addVsyncTimestamp(timestamp);
+ }
+ auto const mNow = *simulatedVsyncs.rbegin();
+ EXPECT_FALSE(tracker.needsMoreSamples(mNow));
+
+ // TODO: would be better to decay this as a result of the variance of the samples
+ static auto constexpr aLongTimeOut = 1000000000;
+ EXPECT_TRUE(tracker.needsMoreSamples(mNow + aLongTimeOut));
+}
+
+TEST_F(VSyncPredictorTest, idealModelPredictionsBeforeRegressionModelIsBuilt) {
+ auto const simulatedVsyncs =
+ generateVsyncTimestamps(kMinimumSamplesForPrediction + 1, mPeriod, 0);
+ nsecs_t const mNow = 0;
+ EXPECT_THAT(tracker.nextAnticipatedVSyncTimeFrom(mNow), Eq(mPeriod));
+
+ nsecs_t const aBitOfTime = 422;
+
+ for (auto i = 0; i < kMinimumSamplesForPrediction; i++) {
+ tracker.addVsyncTimestamp(simulatedVsyncs[i]);
+ EXPECT_THAT(tracker.nextAnticipatedVSyncTimeFrom(simulatedVsyncs[i] + aBitOfTime),
+ Eq(mPeriod + simulatedVsyncs[i]));
+ }
+
+ for (auto i = kMinimumSamplesForPrediction; i < simulatedVsyncs.size(); i++) {
+ tracker.addVsyncTimestamp(simulatedVsyncs[i]);
+ EXPECT_THAT(tracker.nextAnticipatedVSyncTimeFrom(simulatedVsyncs[i] + aBitOfTime),
+ Eq(mPeriod + simulatedVsyncs[i]));
+ }
+}
+
+} // namespace android::scheduler