SF: Short-circuit scheduler content detection

Avoid registering, recording, partitioning, and transforming layers
for content detection in the scheduler if there is a single refresh
rate config.

Dump content detection version, and layer history stats.

Bug: 158780872
Test: No layer history on crosshatch, ARC, etc.
Test: dumpsys SurfaceFlinger --vsync
Test: libsurfaceflinger_unittest
Change-Id: Ia23a35cd6aa0cb117b19c98f5d0af8c14836430e
diff --git a/services/surfaceflinger/Scheduler/LayerHistory.cpp b/services/surfaceflinger/Scheduler/LayerHistory.cpp
index 2925109..cf753a2 100644
--- a/services/surfaceflinger/Scheduler/LayerHistory.cpp
+++ b/services/surfaceflinger/Scheduler/LayerHistory.cpp
@@ -20,6 +20,7 @@
 
 #include "LayerHistory.h"
 
+#include <android-base/stringprintf.h>
 #include <cutils/properties.h>
 #include <utils/Log.h>
 #include <utils/Timers.h>
@@ -180,4 +181,11 @@
 
     mActiveLayersEnd = 0;
 }
+
+std::string LayerHistory::dump() const {
+    std::lock_guard lock(mLock);
+    return base::StringPrintf("LayerHistory{size=%zu, active=%zu}", mLayerInfos.size(),
+                              mActiveLayersEnd);
+}
+
 } // namespace android::scheduler::impl
diff --git a/services/surfaceflinger/Scheduler/LayerHistory.h b/services/surfaceflinger/Scheduler/LayerHistory.h
index 228b8a0..128699b 100644
--- a/services/surfaceflinger/Scheduler/LayerHistory.h
+++ b/services/surfaceflinger/Scheduler/LayerHistory.h
@@ -22,6 +22,7 @@
 
 #include <memory>
 #include <mutex>
+#include <string>
 #include <utility>
 #include <vector>
 
@@ -71,6 +72,7 @@
     virtual Summary summarize(nsecs_t now) = 0;
 
     virtual void clear() = 0;
+    virtual std::string dump() const = 0;
 };
 
 namespace impl {
@@ -97,6 +99,7 @@
     android::scheduler::LayerHistory::Summary summarize(nsecs_t now) override;
 
     void clear() override;
+    std::string dump() const override;
 
 private:
     friend class android::scheduler::LayerHistoryTest;
@@ -155,6 +158,7 @@
     android::scheduler::LayerHistory::Summary summarize(nsecs_t /*now*/) override;
 
     void clear() override;
+    std::string dump() const override;
 
 private:
     friend android::scheduler::LayerHistoryTestV2;
diff --git a/services/surfaceflinger/Scheduler/LayerHistoryV2.cpp b/services/surfaceflinger/Scheduler/LayerHistoryV2.cpp
index ee612b0..e42c5cf 100644
--- a/services/surfaceflinger/Scheduler/LayerHistoryV2.cpp
+++ b/services/surfaceflinger/Scheduler/LayerHistoryV2.cpp
@@ -20,6 +20,7 @@
 
 #include "LayerHistory.h"
 
+#include <android-base/stringprintf.h>
 #include <cutils/properties.h>
 #include <utils/Log.h>
 #include <utils/Timers.h>
@@ -31,9 +32,8 @@
 #include <utility>
 
 #include "../Layer.h"
-#include "SchedulerUtils.h"
-
 #include "LayerInfoV2.h"
+#include "SchedulerUtils.h"
 
 namespace android::scheduler::impl {
 
@@ -213,4 +213,10 @@
     }
 }
 
+std::string LayerHistoryV2::dump() const {
+    std::lock_guard lock(mLock);
+    return base::StringPrintf("LayerHistoryV2{size=%zu, active=%zu}", mLayerInfos.size(),
+                              mActiveLayersEnd);
+}
+
 } // namespace android::scheduler::impl
diff --git a/services/surfaceflinger/Scheduler/RefreshRateConfigs.h b/services/surfaceflinger/Scheduler/RefreshRateConfigs.h
index 8a51b85..4ee7ff3 100644
--- a/services/surfaceflinger/Scheduler/RefreshRateConfigs.h
+++ b/services/surfaceflinger/Scheduler/RefreshRateConfigs.h
@@ -273,6 +273,11 @@
     RefreshRateConfigs(const std::vector<std::shared_ptr<const HWC2::Display::Config>>& configs,
                        HwcConfigIndexType currentConfigId);
 
+    // Returns whether switching configs (refresh rate or resolution) is possible.
+    // TODO(b/158780872): Consider HAL support, and skip frame rate detection if the configs only
+    // differ in resolution.
+    bool canSwitch() const { return mRefreshRates.size() > 1; }
+
     // Class to enumerate options around toggling the kernel timer on and off. We have an option
     // for no change to avoid extra calls to kernel.
     enum class KernelIdleTimerAction {
diff --git a/services/surfaceflinger/Scheduler/Scheduler.cpp b/services/surfaceflinger/Scheduler/Scheduler.cpp
index 5c0ba01..ab63d64 100644
--- a/services/surfaceflinger/Scheduler/Scheduler.cpp
+++ b/services/surfaceflinger/Scheduler/Scheduler.cpp
@@ -61,6 +61,7 @@
     } while (false)
 
 namespace android {
+namespace {
 
 std::unique_ptr<DispSync> createDispSync(bool supportKernelTimer) {
     // TODO (140302863) remove this and use the vsync_reactor system.
@@ -97,25 +98,27 @@
     }
 }
 
+const char* toContentDetectionString(bool useContentDetection, bool useContentDetectionV2) {
+    if (!useContentDetection) return "off";
+    return useContentDetectionV2 ? "V2" : "V1";
+}
+
+} // namespace
+
 Scheduler::Scheduler(impl::EventControlThread::SetVSyncEnabledFunction function,
-                     const scheduler::RefreshRateConfigs& refreshRateConfig,
+                     const scheduler::RefreshRateConfigs& refreshRateConfigs,
                      ISchedulerCallback& schedulerCallback, bool useContentDetectionV2,
                      bool useContentDetection)
       : mSupportKernelTimer(sysprop::support_kernel_idle_timer(false)),
         mPrimaryDispSync(createDispSync(mSupportKernelTimer)),
         mEventControlThread(new impl::EventControlThread(std::move(function))),
+        mLayerHistory(createLayerHistory(refreshRateConfigs, useContentDetectionV2)),
         mSchedulerCallback(schedulerCallback),
-        mRefreshRateConfigs(refreshRateConfig),
+        mRefreshRateConfigs(refreshRateConfigs),
         mUseContentDetection(useContentDetection),
         mUseContentDetectionV2(useContentDetectionV2) {
     using namespace sysprop;
 
-    if (mUseContentDetectionV2) {
-        mLayerHistory = std::make_unique<scheduler::impl::LayerHistoryV2>(refreshRateConfig);
-    } else {
-        mLayerHistory = std::make_unique<scheduler::impl::LayerHistory>();
-    }
-
     const int setIdleTimerMs = property_get_int32("debug.sf.set_idle_timer_ms", 0);
 
     if (const auto millis = setIdleTimerMs ? setIdleTimerMs : set_idle_timer_ms(0); millis > 0) {
@@ -149,11 +152,13 @@
 Scheduler::Scheduler(std::unique_ptr<DispSync> primaryDispSync,
                      std::unique_ptr<EventControlThread> eventControlThread,
                      const scheduler::RefreshRateConfigs& configs,
-                     ISchedulerCallback& schedulerCallback, bool useContentDetectionV2,
+                     ISchedulerCallback& schedulerCallback,
+                     std::unique_ptr<LayerHistory> layerHistory, bool useContentDetectionV2,
                      bool useContentDetection)
       : mSupportKernelTimer(false),
         mPrimaryDispSync(std::move(primaryDispSync)),
         mEventControlThread(std::move(eventControlThread)),
+        mLayerHistory(std::move(layerHistory)),
         mSchedulerCallback(schedulerCallback),
         mRefreshRateConfigs(configs),
         mUseContentDetection(useContentDetection),
@@ -166,6 +171,17 @@
     mIdleTimer.reset();
 }
 
+std::unique_ptr<LayerHistory> Scheduler::createLayerHistory(
+        const scheduler::RefreshRateConfigs& configs, bool useContentDetectionV2) {
+    if (!configs.canSwitch()) return nullptr;
+
+    if (useContentDetectionV2) {
+        return std::make_unique<scheduler::impl::LayerHistoryV2>(configs);
+    }
+
+    return std::make_unique<scheduler::impl::LayerHistory>();
+}
+
 DispSync& Scheduler::getPrimaryDispSync() {
     return *mPrimaryDispSync;
 }
@@ -499,16 +515,7 @@
 }
 
 void Scheduler::notifyTouchEvent() {
-    if (!mTouchTimer) return;
-
-    // Touch event will boost the refresh rate to performance.
-    // Clear Layer History to get fresh FPS detection.
-    // NOTE: Instead of checking all the layers, we should be checking the layer
-    // that is currently on top. b/142507166 will give us this capability.
-    std::lock_guard<std::mutex> lock(mFeatureStateLock);
-    if (mLayerHistory) {
-        // Layer History will be cleared based on RefreshRateConfigs::getBestRefreshRate
-
+    if (mTouchTimer) {
         mTouchTimer->reset();
 
         if (mSupportKernelTimer && mIdleTimer) {
@@ -564,8 +571,14 @@
 
 void Scheduler::touchTimerCallback(TimerState state) {
     const TouchState touch = state == TimerState::Reset ? TouchState::Active : TouchState::Inactive;
+    // Touch event will boost the refresh rate to performance.
+    // Clear layer history to get fresh FPS detection.
+    // NOTE: Instead of checking all the layers, we should be checking the layer
+    // that is currently on top. b/142507166 will give us this capability.
     if (handleTimerStateChanged(&mFeatures.touch, touch)) {
-        mLayerHistory->clear();
+        if (mLayerHistory) {
+            mLayerHistory->clear();
+        }
     }
     ATRACE_INT("TouchState", static_cast<int>(touch));
 }
@@ -577,14 +590,13 @@
 
 void Scheduler::dump(std::string& result) const {
     using base::StringAppendF;
-    const char* const states[] = {"off", "on"};
 
-    StringAppendF(&result, "+  Idle timer: %s\n",
-                  mIdleTimer ? mIdleTimer->dump().c_str() : states[0]);
+    StringAppendF(&result, "+  Idle timer: %s\n", mIdleTimer ? mIdleTimer->dump().c_str() : "off");
     StringAppendF(&result, "+  Touch timer: %s\n",
-                  mTouchTimer ? mTouchTimer->dump().c_str() : states[0]);
-    StringAppendF(&result, "+  Use content detection: %s\n\n",
-                  sysprop::use_content_detection_for_refresh_rate(false) ? "on" : "off");
+                  mTouchTimer ? mTouchTimer->dump().c_str() : "off");
+    StringAppendF(&result, "+  Content detection: %s %s\n\n",
+                  toContentDetectionString(mUseContentDetection, mUseContentDetectionV2),
+                  mLayerHistory ? mLayerHistory->dump().c_str() : "(no layer history)");
 }
 
 template <class T>
diff --git a/services/surfaceflinger/Scheduler/Scheduler.h b/services/surfaceflinger/Scheduler/Scheduler.h
index 730ea8f..5fee4b4 100644
--- a/services/surfaceflinger/Scheduler/Scheduler.h
+++ b/services/surfaceflinger/Scheduler/Scheduler.h
@@ -174,8 +174,11 @@
 
     // Used by tests to inject mocks.
     Scheduler(std::unique_ptr<DispSync>, std::unique_ptr<EventControlThread>,
-              const scheduler::RefreshRateConfigs&, ISchedulerCallback& schedulerCallback,
-              bool useContentDetectionV2, bool useContentDetection);
+              const scheduler::RefreshRateConfigs&, ISchedulerCallback&,
+              std::unique_ptr<LayerHistory>, bool useContentDetectionV2, bool useContentDetection);
+
+    static std::unique_ptr<LayerHistory> createLayerHistory(const scheduler::RefreshRateConfigs&,
+                                                            bool useContentDetectionV2);
 
     std::unique_ptr<VSyncSource> makePrimaryDispSyncSource(const char* name, nsecs_t phaseOffsetNs);
 
@@ -231,7 +234,7 @@
     std::unique_ptr<EventControlThread> mEventControlThread;
 
     // Used to choose refresh rate if content detection is enabled.
-    std::unique_ptr<LayerHistory> mLayerHistory;
+    const std::unique_ptr<LayerHistory> mLayerHistory;
 
     // Timer that records time between requests for next vsync.
     std::optional<scheduler::OneShotTimer> mIdleTimer;