SF: Simplify getBestRefreshRate caching

Cache the arguments/result as std::pair by removing the out parameter
for GlobalSignals.

Bug: 185535769
Test: libsurfaceflinger_unittest
Change-Id: Ibfb2aa4ca327b378844554bcd96620f84fc0460a
diff --git a/services/surfaceflinger/Scheduler/RefreshRateConfigs.cpp b/services/surfaceflinger/Scheduler/RefreshRateConfigs.cpp
index 3becb5c..3b9cfa6 100644
--- a/services/surfaceflinger/Scheduler/RefreshRateConfigs.cpp
+++ b/services/surfaceflinger/Scheduler/RefreshRateConfigs.cpp
@@ -38,6 +38,8 @@
 namespace android::scheduler {
 namespace {
 
+constexpr RefreshRateConfigs::GlobalSignals kNoSignals;
+
 std::string formatLayerInfo(const RefreshRateConfigs::LayerRequirement& layer, float weight) {
     return base::StringPrintf("%s (type=%s, weight=%.2f seamlessness=%s) %s", layer.name.c_str(),
                               ftl::enum_string(layer.vote).c_str(), weight,
@@ -235,63 +237,26 @@
     float score;
 };
 
-RefreshRate RefreshRateConfigs::getBestRefreshRate(const std::vector<LayerRequirement>& layers,
-                                                   GlobalSignals globalSignals,
-                                                   GlobalSignals* outSignalsConsidered) const {
+auto RefreshRateConfigs::getBestRefreshRate(const std::vector<LayerRequirement>& layers,
+                                            GlobalSignals signals) const
+        -> std::pair<RefreshRate, GlobalSignals> {
     std::lock_guard lock(mLock);
 
-    if (auto cached = getCachedBestRefreshRate(layers, globalSignals, outSignalsConsidered)) {
-        return *cached;
+    if (mGetBestRefreshRateCache &&
+        mGetBestRefreshRateCache->arguments == std::make_pair(layers, signals)) {
+        return mGetBestRefreshRateCache->result;
     }
 
-    GlobalSignals signalsConsidered;
-    RefreshRate result = getBestRefreshRateLocked(layers, globalSignals, &signalsConsidered);
-    lastBestRefreshRateInvocation.emplace(
-            GetBestRefreshRateInvocation{.layerRequirements = layers,
-                                         .globalSignals = globalSignals,
-                                         .outSignalsConsidered = signalsConsidered,
-                                         .resultingBestRefreshRate = result});
-    if (outSignalsConsidered) {
-        *outSignalsConsidered = signalsConsidered;
-    }
+    const auto result = getBestRefreshRateLocked(layers, signals);
+    mGetBestRefreshRateCache = GetBestRefreshRateCache{{layers, signals}, result};
     return result;
 }
 
-std::optional<RefreshRate> RefreshRateConfigs::getCachedBestRefreshRate(
-        const std::vector<LayerRequirement>& layers, GlobalSignals globalSignals,
-        GlobalSignals* outSignalsConsidered) const {
-    const bool sameAsLastCall = lastBestRefreshRateInvocation &&
-            lastBestRefreshRateInvocation->layerRequirements == layers &&
-            lastBestRefreshRateInvocation->globalSignals == globalSignals;
-
-    if (sameAsLastCall) {
-        if (outSignalsConsidered) {
-            *outSignalsConsidered = lastBestRefreshRateInvocation->outSignalsConsidered;
-        }
-        return lastBestRefreshRateInvocation->resultingBestRefreshRate;
-    }
-
-    return {};
-}
-
-RefreshRate RefreshRateConfigs::getBestRefreshRateLocked(
-        const std::vector<LayerRequirement>& layers, GlobalSignals globalSignals,
-        GlobalSignals* outSignalsConsidered) const {
+auto RefreshRateConfigs::getBestRefreshRateLocked(const std::vector<LayerRequirement>& layers,
+                                                  GlobalSignals signals) const
+        -> std::pair<RefreshRate, GlobalSignals> {
     ATRACE_CALL();
-    ALOGV("getBestRefreshRate %zu layers", layers.size());
-
-    if (outSignalsConsidered) *outSignalsConsidered = {};
-    const auto setTouchConsidered = [&] {
-        if (outSignalsConsidered) {
-            outSignalsConsidered->touch = true;
-        }
-    };
-
-    const auto setIdleConsidered = [&] {
-        if (outSignalsConsidered) {
-            outSignalsConsidered->idle = true;
-        }
-    };
+    ALOGV("%s: %zu layers", __func__, layers.size());
 
     int noVoteLayers = 0;
     int minVoteLayers = 0;
@@ -301,6 +266,7 @@
     int explicitExact = 0;
     float maxExplicitWeight = 0;
     int seamedFocusedLayers = 0;
+
     for (const auto& layer : layers) {
         switch (layer.vote) {
             case LayerVoteType::NoVote:
@@ -349,10 +315,9 @@
 
     // Consider the touch event if there are no Explicit* layers. Otherwise wait until after we've
     // selected a refresh rate to see if we should apply touch boost.
-    if (globalSignals.touch && !hasExplicitVoteLayers) {
+    if (signals.touch && !hasExplicitVoteLayers) {
         ALOGV("TouchBoost - choose %s", getMaxRefreshRateByPolicyLocked().getName().c_str());
-        setTouchConsidered();
-        return getMaxRefreshRateByPolicyLocked(anchorGroup);
+        return {getMaxRefreshRateByPolicyLocked(anchorGroup), GlobalSignals{.touch = true}};
     }
 
     // If the primary range consists of a single refresh rate then we can only
@@ -361,23 +326,21 @@
     const bool primaryRangeIsSingleRate =
             isApproxEqual(policy->primaryRange.min, policy->primaryRange.max);
 
-    if (!globalSignals.touch && globalSignals.idle &&
-        !(primaryRangeIsSingleRate && hasExplicitVoteLayers)) {
+    if (!signals.touch && signals.idle && !(primaryRangeIsSingleRate && hasExplicitVoteLayers)) {
         ALOGV("Idle - choose %s", getMinRefreshRateByPolicyLocked().getName().c_str());
-        setIdleConsidered();
-        return getMinRefreshRateByPolicyLocked();
+        return {getMinRefreshRateByPolicyLocked(), GlobalSignals{.idle = true}};
     }
 
     if (layers.empty() || noVoteLayers == layers.size()) {
         const auto& refreshRate = getMaxRefreshRateByPolicyLocked(anchorGroup);
         ALOGV("no layers with votes - choose %s", refreshRate.getName().c_str());
-        return refreshRate;
+        return {refreshRate, kNoSignals};
     }
 
     // Only if all layers want Min we should return Min
     if (noVoteLayers + minVoteLayers == layers.size()) {
         ALOGV("all layers Min - choose %s", getMinRefreshRateByPolicyLocked().getName().c_str());
-        return getMinRefreshRateByPolicyLocked();
+        return {getMinRefreshRateByPolicyLocked(), kNoSignals};
     }
 
     // Find the best refresh rate based on score
@@ -466,9 +429,9 @@
                         [](RefreshRateScore score) { return score.score == 0; })) {
             const auto& refreshRate = getMaxRefreshRateByPolicyLocked(anchorGroup);
             ALOGV("layers not scored - choose %s", refreshRate.getName().c_str());
-            return refreshRate;
+            return {refreshRate, kNoSignals};
         } else {
-            return *bestRefreshRate;
+            return {*bestRefreshRate, kNoSignals};
         }
     }
 
@@ -490,14 +453,13 @@
 
     using fps_approx_ops::operator<;
 
-    if (globalSignals.touch && explicitDefaultVoteLayers == 0 && touchBoostForExplicitExact &&
+    if (signals.touch && explicitDefaultVoteLayers == 0 && touchBoostForExplicitExact &&
         bestRefreshRate->getFps() < touchRefreshRate.getFps()) {
-        setTouchConsidered();
         ALOGV("TouchBoost - choose %s", touchRefreshRate.getName().c_str());
-        return touchRefreshRate;
+        return {touchRefreshRate, GlobalSignals{.touch = true}};
     }
 
-    return *bestRefreshRate;
+    return {*bestRefreshRate, kNoSignals};
 }
 
 std::unordered_map<uid_t, std::vector<const RefreshRateConfigs::LayerRequirement*>>
@@ -699,7 +661,7 @@
 
     // Invalidate the cached invocation to getBestRefreshRate. This forces
     // the refresh rate to be recomputed on the next call to getBestRefreshRate.
-    lastBestRefreshRateInvocation.reset();
+    mGetBestRefreshRateCache.reset();
 
     mCurrentRefreshRate = mRefreshRates.at(modeId).get();
 }
@@ -741,7 +703,7 @@
 
     // Invalidate the cached invocation to getBestRefreshRate. This forces
     // the refresh rate to be recomputed on the next call to getBestRefreshRate.
-    lastBestRefreshRateInvocation.reset();
+    mGetBestRefreshRateCache.reset();
 
     mRefreshRates.clear();
     for (const auto& mode : modes) {
@@ -800,7 +762,7 @@
         ALOGE("Invalid refresh rate policy: %s", policy.toString().c_str());
         return BAD_VALUE;
     }
-    lastBestRefreshRateInvocation.reset();
+    mGetBestRefreshRateCache.reset();
     Policy previousPolicy = *getCurrentPolicyLocked();
     mDisplayManagerPolicy = policy;
     if (*getCurrentPolicyLocked() == previousPolicy) {
@@ -815,7 +777,7 @@
     if (policy && !isPolicyValidLocked(*policy)) {
         return BAD_VALUE;
     }
-    lastBestRefreshRateInvocation.reset();
+    mGetBestRefreshRateCache.reset();
     Policy previousPolicy = *getCurrentPolicyLocked();
     mOverridePolicy = policy;
     if (*getCurrentPolicyLocked() == previousPolicy) {
diff --git a/services/surfaceflinger/Scheduler/RefreshRateConfigs.h b/services/surfaceflinger/Scheduler/RefreshRateConfigs.h
index 7ef95f9..ade1787 100644
--- a/services/surfaceflinger/Scheduler/RefreshRateConfigs.h
+++ b/services/surfaceflinger/Scheduler/RefreshRateConfigs.h
@@ -20,6 +20,7 @@
 #include <numeric>
 #include <optional>
 #include <type_traits>
+#include <utility>
 
 #include <android-base/stringprintf.h>
 #include <gui/DisplayEventReceiver.h>
@@ -249,11 +250,10 @@
         }
     };
 
-    // Returns the refresh rate that best fits the given layers. outSignalsConsidered returns
-    // whether the refresh rate was chosen based on touch boost and/or idle timer.
-    RefreshRate getBestRefreshRate(const std::vector<LayerRequirement>&, GlobalSignals,
-                                   GlobalSignals* outSignalsConsidered = nullptr) const
-            EXCLUDES(mLock);
+    // Returns the refresh rate that best fits the given layers, and whether the refresh rate was
+    // chosen based on touch boost and/or idle timer.
+    std::pair<RefreshRate, GlobalSignals> getBestRefreshRate(const std::vector<LayerRequirement>&,
+                                                             GlobalSignals) const EXCLUDES(mLock);
 
     FpsRange getSupportedRefreshRateRange() const EXCLUDES(mLock) {
         std::lock_guard lock(mLock);
@@ -403,13 +403,8 @@
             const std::function<bool(const RefreshRate&)>& shouldAddRefreshRate,
             std::vector<const RefreshRate*>* outRefreshRates) REQUIRES(mLock);
 
-    std::optional<RefreshRate> getCachedBestRefreshRate(const std::vector<LayerRequirement>&,
-                                                        GlobalSignals,
-                                                        GlobalSignals* outSignalsConsidered) const
-            REQUIRES(mLock);
-
-    RefreshRate getBestRefreshRateLocked(const std::vector<LayerRequirement>&, GlobalSignals,
-                                         GlobalSignals* outSignalsConsidered) const REQUIRES(mLock);
+    std::pair<RefreshRate, GlobalSignals> getBestRefreshRateLocked(
+            const std::vector<LayerRequirement>&, GlobalSignals) const REQUIRES(mLock);
 
     // Returns the refresh rate with the highest score in the collection specified from begin
     // to end. If there are more than one with the same highest refresh rate, the first one is
@@ -497,14 +492,11 @@
     const Config mConfig;
     bool mSupportsFrameRateOverrideByContent;
 
-    struct GetBestRefreshRateInvocation {
-        std::vector<LayerRequirement> layerRequirements;
-        GlobalSignals globalSignals;
-        GlobalSignals outSignalsConsidered;
-        RefreshRate resultingBestRefreshRate;
+    struct GetBestRefreshRateCache {
+        std::pair<std::vector<LayerRequirement>, GlobalSignals> arguments;
+        std::pair<RefreshRate, GlobalSignals> result;
     };
-    mutable std::optional<GetBestRefreshRateInvocation> lastBestRefreshRateInvocation
-            GUARDED_BY(mLock);
+    mutable std::optional<GetBestRefreshRateCache> mGetBestRefreshRateCache GUARDED_BY(mLock);
 
     // Declare mIdleTimer last to ensure its thread joins before the mutex/callbacks are destroyed.
     std::mutex mIdleTimerCallbacksMutex;
diff --git a/services/surfaceflinger/Scheduler/Scheduler.cpp b/services/surfaceflinger/Scheduler/Scheduler.cpp
index a85e748..665d36982 100644
--- a/services/surfaceflinger/Scheduler/Scheduler.cpp
+++ b/services/surfaceflinger/Scheduler/Scheduler.cpp
@@ -537,18 +537,19 @@
 
     ATRACE_CALL();
 
-    const auto refreshRateConfigs = holdRefreshRateConfigs();
-    scheduler::LayerHistory::Summary summary =
-            mLayerHistory.summarize(*refreshRateConfigs, systemTime());
-    scheduler::RefreshRateConfigs::GlobalSignals consideredSignals;
     DisplayModePtr newMode;
+    GlobalSignals consideredSignals;
+
     bool frameRateChanged;
     bool frameRateOverridesChanged;
+
+    const auto refreshRateConfigs = holdRefreshRateConfigs();
+    LayerHistory::Summary summary = mLayerHistory.summarize(*refreshRateConfigs, systemTime());
     {
         std::lock_guard<std::mutex> lock(mPolicyLock);
-        mPolicy.contentRequirements = summary;
+        mPolicy.contentRequirements = std::move(summary);
 
-        newMode = calculateRefreshRateModeId(&consideredSignals);
+        std::tie(newMode, consideredSignals) = chooseDisplayMode();
         frameRateOverridesChanged = updateFrameRateOverrides(consideredSignals, newMode->getFps());
 
         if (mPolicy.mode == newMode) {
@@ -678,8 +679,7 @@
     mVsyncSchedule->dump(out);
 }
 
-bool Scheduler::updateFrameRateOverrides(
-        scheduler::RefreshRateConfigs::GlobalSignals consideredSignals, Fps displayRefreshRate) {
+bool Scheduler::updateFrameRateOverrides(GlobalSignals consideredSignals, Fps displayRefreshRate) {
     const auto refreshRateConfigs = holdRefreshRateConfigs();
     if (!refreshRateConfigs->supportsFrameRateOverrideByContent()) {
         return false;
@@ -697,9 +697,11 @@
 template <class T>
 bool Scheduler::handleTimerStateChanged(T* currentState, T newState) {
     DisplayModePtr newMode;
+    GlobalSignals consideredSignals;
+
     bool refreshRateChanged = false;
     bool frameRateOverridesChanged;
-    scheduler::RefreshRateConfigs::GlobalSignals consideredSignals;
+
     const auto refreshRateConfigs = holdRefreshRateConfigs();
     {
         std::lock_guard<std::mutex> lock(mPolicyLock);
@@ -707,7 +709,7 @@
             return false;
         }
         *currentState = newState;
-        newMode = calculateRefreshRateModeId(&consideredSignals);
+        std::tie(newMode, consideredSignals) = chooseDisplayMode();
         frameRateOverridesChanged = updateFrameRateOverrides(consideredSignals, newMode->getFps());
         if (mPolicy.mode == newMode) {
             // We don't need to change the display mode, but we might need to send an event
@@ -733,33 +735,33 @@
     return consideredSignals.touch;
 }
 
-DisplayModePtr Scheduler::calculateRefreshRateModeId(
-        scheduler::RefreshRateConfigs::GlobalSignals* consideredSignals) {
+auto Scheduler::chooseDisplayMode() -> std::pair<DisplayModePtr, GlobalSignals> {
     ATRACE_CALL();
-    if (consideredSignals) *consideredSignals = {};
 
-    const auto refreshRateConfigs = holdRefreshRateConfigs();
+    const auto configs = holdRefreshRateConfigs();
+
     // If Display Power is not in normal operation we want to be in performance mode. When coming
     // back to normal mode, a grace period is given with DisplayPowerTimer.
     if (mDisplayPowerTimer &&
         (!mPolicy.isDisplayPowerStateNormal || mPolicy.displayPowerTimer == TimerState::Reset)) {
-        return refreshRateConfigs->getMaxRefreshRateByPolicy().getMode();
+        constexpr GlobalSignals kNoSignals;
+        return {configs->getMaxRefreshRateByPolicy().getMode(), kNoSignals};
     }
 
-    const bool touchActive = mTouchTimer && mPolicy.touch == TouchState::Active;
-    const bool idle = mPolicy.idleTimer == TimerState::Expired;
+    const GlobalSignals signals{.touch = mTouchTimer && mPolicy.touch == TouchState::Active,
+                                .idle = mPolicy.idleTimer == TimerState::Expired};
 
-    return refreshRateConfigs
-            ->getBestRefreshRate(mPolicy.contentRequirements, {.touch = touchActive, .idle = idle},
-                                 consideredSignals)
-            .getMode();
+    const auto [refreshRate, consideredSignals] =
+            configs->getBestRefreshRate(mPolicy.contentRequirements, signals);
+
+    return {refreshRate.getMode(), consideredSignals};
 }
 
 DisplayModePtr Scheduler::getPreferredDisplayMode() {
     std::lock_guard<std::mutex> lock(mPolicyLock);
-    // Make sure that the default mode ID is first updated, before returned.
+    // Make sure the stored mode is up to date.
     if (mPolicy.mode) {
-        mPolicy.mode = calculateRefreshRateModeId();
+        mPolicy.mode = chooseDisplayMode().first;
     }
     return mPolicy.mode;
 }
diff --git a/services/surfaceflinger/Scheduler/Scheduler.h b/services/surfaceflinger/Scheduler/Scheduler.h
index bc9024a..468c4cc 100644
--- a/services/surfaceflinger/Scheduler/Scheduler.h
+++ b/services/surfaceflinger/Scheduler/Scheduler.h
@@ -269,15 +269,14 @@
 
     void setVsyncPeriod(nsecs_t period);
 
-    // This function checks whether individual features that are affecting the refresh rate
-    // selection were initialized, prioritizes them, and calculates the DisplayModeId
-    // for the suggested refresh rate.
-    DisplayModePtr calculateRefreshRateModeId(
-            RefreshRateConfigs::GlobalSignals* consideredSignals = nullptr) REQUIRES(mPolicyLock);
+    using GlobalSignals = RefreshRateConfigs::GlobalSignals;
+
+    // Returns the display mode that fulfills the policy, and the signals that were considered.
+    std::pair<DisplayModePtr, GlobalSignals> chooseDisplayMode() REQUIRES(mPolicyLock);
+
+    bool updateFrameRateOverrides(GlobalSignals, Fps displayRefreshRate) REQUIRES(mPolicyLock);
 
     void dispatchCachedReportedMode() REQUIRES(mPolicyLock) EXCLUDES(mRefreshRateConfigsLock);
-    bool updateFrameRateOverrides(RefreshRateConfigs::GlobalSignals, Fps displayRefreshRate)
-            REQUIRES(mPolicyLock);
 
     impl::EventThread::ThrottleVsyncCallback makeThrottleVsyncCallback() const
             EXCLUDES(mRefreshRateConfigsLock);