SurfaceFlinger: refactor frame time tracking

This change moves the frame time history tracking code out of Layer and into a
new class called FrameTracker.  It also changes the tracking to use signal
timestamps from fences when available for more accurate results.

Change-Id: I323c5f075c58bf86ce363b52af885ad0f6365f2b

include/ui/Fence.h

@@ -25,6 +25,7 @@
 #include <ui/Rect.h>
 #include <utils/Flattenable.h>
 #include <utils/String8.h>
+#include <utils/Timers.h>
 
 struct ANativeWindowBuffer;
 
@@ -40,6 +41,10 @@ class Fence
 public:
     static const sp<Fence> NO_FENCE;
 
+    // TIMEOUT_NEVER may be passed to the wait method to indicate that it
+    // should wait indefinitely for the fence to signal.
+    enum { TIMEOUT_NEVER = -1 };
+
     // Construct a new Fence object with an invalid file descriptor.  This
     // should be done when the Fence object will be set up by unflattening
     // serialized data.
@@ -69,10 +74,6 @@ public:
     // the caller and will be included in the log message.
     status_t waitForever(unsigned int warningTimeout, const char* logname);
 
-    // TIMEOUT_NEVER may be passed to the wait method to indicate that it
-    // should wait indefinitely for the fence to signal.
-    enum { TIMEOUT_NEVER = -1 };
-
     // merge combines two Fence objects, creating a new Fence object that
     // becomes signaled when both f1 and f2 are signaled (even if f1 or f2 is
     // destroyed before it becomes signaled).  The name argument specifies the
@@ -85,6 +86,12 @@ public:
     // be returned and errno will indicate the problem.
     int dup() const;
 
+    // getSignalTime returns the system monotonic clock time at which the
+    // fence transitioned to the signaled state.  If the fence is not signaled
+    // then INT64_MAX is returned.  If the fence is invalid or if an error
+    // occurs then -1 is returned.
+    nsecs_t getSignalTime() const;
+
     // Flattenable interface
     size_t getFlattenedSize() const;
     size_t getFdCount() const;

libs/ui/Fence.cpp

@@ -18,6 +18,9 @@
 #define ATRACE_TAG ATRACE_TAG_GRAPHICS
 //#define LOG_NDEBUG 0
 
+ // This is needed for stdint.h to define INT64_MAX in C++
+ #define __STDC_LIMIT_MACROS
+
 #include <sync/sync.h>
 #include <ui/Fence.h>
 #include <unistd.h>
@@ -86,6 +89,32 @@ int Fence::dup() const {
     return ::dup(mFenceFd);
 }
 
+nsecs_t Fence::getSignalTime() const {
+    if (mFenceFd == -1) {
+        return -1;
+    }
+
+    struct sync_fence_info_data* finfo = sync_fence_info(mFenceFd);
+    if (finfo == NULL) {
+        ALOGE("sync_fence_info returned NULL for fd %d", mFenceFd);
+        return -1;
+    }
+    if (finfo->status != 1) {
+        return INT64_MAX;
+    }
+
+    struct sync_pt_info* pinfo = NULL;
+    uint64_t timestamp = 0;
+    while ((pinfo = sync_pt_info(finfo, pinfo)) != NULL) {
+        if (pinfo->timestamp_ns > timestamp) {
+            timestamp = pinfo->timestamp_ns;
+        }
+    }
+    sync_fence_info_free(finfo);
+
+    return nsecs_t(timestamp);
+}
+
 size_t Fence::getFlattenedSize() const {
     return 0;
 }

services/surfaceflinger/Android.mk

@@ -5,6 +5,7 @@ LOCAL_SRC_FILES:= \
     Client.cpp                              \
     DisplayDevice.cpp                       \
     EventThread.cpp                         \
+    FrameTracker.cpp                        \
     Layer.cpp                               \
     LayerBase.cpp                           \
     LayerDim.cpp                            \

services/surfaceflinger/FrameTracker.cpp

@@ -0,0 +1,132 @@
+/*
+ * Copyright (C) 2012 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.
+ */
+
+// This is needed for stdint.h to define INT64_MAX in C++
+#define __STDC_LIMIT_MACROS
+
+#include <ui/Fence.h>
+
+#include <utils/String8.h>
+
+#include "FrameTracker.h"
+
+namespace android {
+
+FrameTracker::FrameTracker() :
+        mOffset(0),
+        mNumFences(0) {
+}
+
+void FrameTracker::setDesiredPresentTime(nsecs_t presentTime) {
+    mFrameRecords[mOffset].desiredPresentTime = presentTime;
+}
+
+void FrameTracker::setFrameReadyTime(nsecs_t readyTime) {
+    mFrameRecords[mOffset].frameReadyTime = readyTime;
+}
+
+void FrameTracker::setFrameReadyFence(const sp<Fence>& readyFence) {
+    mFrameRecords[mOffset].frameReadyFence = readyFence;
+    mNumFences++;
+}
+
+void FrameTracker::setActualPresentTime(nsecs_t presentTime) {
+    mFrameRecords[mOffset].actualPresentTime = presentTime;
+}
+
+void FrameTracker::setActualPresentFence(const sp<Fence>& readyFence) {
+    mFrameRecords[mOffset].actualPresentFence = readyFence;
+    mNumFences++;
+}
+
+void FrameTracker::advanceFrame() {
+    mOffset = (mOffset+1) % NUM_FRAME_RECORDS;
+    mFrameRecords[mOffset].desiredPresentTime = INT64_MAX;
+    mFrameRecords[mOffset].frameReadyTime = INT64_MAX;
+    mFrameRecords[mOffset].actualPresentTime = INT64_MAX;
+
+    if (mFrameRecords[mOffset].frameReadyFence != NULL) {
+        // We're clobbering an unsignaled fence, so we need to decrement the
+        // fence count.
+        mFrameRecords[mOffset].frameReadyFence = NULL;
+        mNumFences--;
+    }
+
+    if (mFrameRecords[mOffset].actualPresentFence != NULL) {
+        // We're clobbering an unsignaled fence, so we need to decrement the
+        // fence count.
+        mFrameRecords[mOffset].actualPresentFence = NULL;
+        mNumFences--;
+    }
+
+    // Clean up the signaled fences to keep the number of open fence FDs in
+    // this process reasonable.
+    processFences();
+}
+
+void FrameTracker::clear() {
+    for (size_t i = 0; i < NUM_FRAME_RECORDS; i++) {
+        mFrameRecords[i].desiredPresentTime = 0;
+        mFrameRecords[i].frameReadyTime = 0;
+        mFrameRecords[i].actualPresentTime = 0;
+        mFrameRecords[i].frameReadyFence.clear();
+        mFrameRecords[i].actualPresentFence.clear();
+    }
+    mNumFences = 0;
+}
+
+void FrameTracker::processFences() const {
+    FrameRecord* records = const_cast<FrameRecord*>(mFrameRecords);
+    int& numFences = const_cast<int&>(mNumFences);
+
+    for (int i = 1; i < NUM_FRAME_RECORDS && numFences > 0; i++) {
+        size_t idx = (mOffset+NUM_FRAME_RECORDS-i) % NUM_FRAME_RECORDS;
+
+        const sp<Fence>& rfence = records[idx].frameReadyFence;
+        if (rfence != NULL) {
+            records[idx].frameReadyTime = rfence->getSignalTime();
+            if (records[idx].frameReadyTime < INT64_MAX) {
+                records[idx].frameReadyFence = NULL;
+                numFences--;
+            }
+        }
+
+        const sp<Fence>& pfence = records[idx].actualPresentFence;
+        if (pfence != NULL) {
+            records[idx].actualPresentTime = pfence->getSignalTime();
+            if (records[idx].actualPresentTime < INT64_MAX) {
+                records[idx].actualPresentFence = NULL;
+                numFences--;
+            }
+        }
+    }
+}
+
+void FrameTracker::dump(String8& result) const {
+    processFences();
+
+    const size_t o = mOffset;
+    for (size_t i = 1; i < NUM_FRAME_RECORDS; i++) {
+        const size_t index = (o+i) % NUM_FRAME_RECORDS;
+        result.appendFormat("%lld\t%lld\t%lld\n",
+            mFrameRecords[index].desiredPresentTime,
+            mFrameRecords[index].actualPresentTime,
+            mFrameRecords[index].frameReadyTime);
+    }
+    result.append("\n");
+}
+
+} // namespace android

services/surfaceflinger/FrameTracker.h

@@ -0,0 +1,120 @@
+/*
+ * Copyright (C) 2012 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.
+ */
+
+#ifndef ANDROID_FRAMETRACKER_H
+#define ANDROID_FRAMETRACKER_H
+
+#include <stddef.h>
+
+#include <utils/Timers.h>
+#include <utils/RefBase.h>
+
+namespace android {
+
+class String8;
+class Fence;
+
+// FrameTracker tracks information about the most recently rendered frames. It
+// uses a circular buffer of frame records, and is *NOT* thread-safe -
+// mutexing must be done at a higher level if multi-threaded access is
+// possible.
+//
+// Some of the time values tracked may be set either as a specific timestamp
+// or a fence.  When a non-NULL fence is set for a given time value, the
+// signal time of that fence is used instead of the timestamp.
+class FrameTracker {
+
+public:
+    // NUM_FRAME_RECORDS is the size of the circular buffer used to track the
+    // frame time history.
+    enum { NUM_FRAME_RECORDS = 128 };
+
+    FrameTracker();
+
+    // setDesiredPresentTime sets the time at which the current frame
+    // should be presented to the user under ideal (i.e. zero latency)
+    // conditions.
+    void setDesiredPresentTime(nsecs_t desiredPresentTime);
+
+    // setFrameReadyTime sets the time at which the current frame became ready
+    // to be presented to the user.  For example, if the frame contents is
+    // being written to memory by some asynchronous hardware, this would be
+    // the time at which those writes completed.
+    void setFrameReadyTime(nsecs_t readyTime);
+
+    // setFrameReadyFence sets the fence that is used to get the time at which
+    // the current frame became ready to be presented to the user.
+    void setFrameReadyFence(const sp<Fence>& readyFence);
+
+    // setActualPresentTime sets the timestamp at which the current frame became
+    // visible to the user.
+    void setActualPresentTime(nsecs_t displayTime);
+
+    // setActualPresentFence sets the fence that is used to get the time
+    // at which the current frame became visible to the user.
+    void setActualPresentFence(const sp<Fence>& fence);
+
+    // advanceFrame advances the frame tracker to the next frame.
+    void advanceFrame();
+
+    // clear resets all the tracked frame data to zero.
+    void clear();
+
+    // dump appends the current frame display time history to the result string.
+    void dump(String8& result) const;
+
+private:
+    struct FrameRecord {
+        FrameRecord() :
+            desiredPresentTime(0),
+            frameReadyTime(0),
+            actualPresentTime(0) {}
+        nsecs_t desiredPresentTime;
+        nsecs_t frameReadyTime;
+        nsecs_t actualPresentTime;
+        sp<Fence> frameReadyFence;
+        sp<Fence> actualPresentFence;
+    };
+
+    // processFences iterates over all the frame records that have a fence set
+    // and replaces that fence with a timestamp if the fence has signaled.  If
+    // the fence is not signaled the record's displayTime is set to INT64_MAX.
+    //
+    // This method is const because although it modifies the frame records it
+    // does so in such a way that the information represented should not
+    // change.  This allows it to be called from the dump method.
+    void processFences() const;
+
+    // mFrameRecords is the circular buffer storing the tracked data for each
+    // frame.
+    FrameRecord mFrameRecords[NUM_FRAME_RECORDS];
+
+    // mOffset is the offset into mFrameRecords of the current frame.
+    size_t mOffset;
+
+    // mNumFences is the total number of fences set in the frame records.  It
+    // is incremented each time a fence is added and decremented each time a
+    // signaled fence is removed in processFences or if advanceFrame clobbers
+    // a fence.
+    //
+    // The number of fences is tracked so that the run time of processFences
+    // doesn't grow with NUM_FRAME_RECORDS.
+    int mNumFences;
+};
+
+}
+
+#endif // ANDROID_FRAMETRACKER_H

services/surfaceflinger/Layer.cpp

@@ -59,7 +59,6 @@ Layer::Layer(SurfaceFlinger* flinger, const sp<Client>& client)
         mCurrentOpacity(true),
         mRefreshPending(false),
         mFrameLatencyNeeded(false),
-        mFrameLatencyOffset(0),
         mFormat(PIXEL_FORMAT_NONE),
         mGLExtensions(GLExtensions::getInstance()),
         mOpaqueLayer(true),
@@ -507,12 +506,30 @@ bool Layer::onPreComposition() {
 
 void Layer::onPostComposition() {
     if (mFrameLatencyNeeded) {
+        nsecs_t desiredPresentTime = mSurfaceTexture->getTimestamp();
+        mFrameTracker.setDesiredPresentTime(desiredPresentTime);
+
+        sp<Fence> frameReadyFence = mSurfaceTexture->getCurrentFence();
+        if (frameReadyFence != NULL) {
+            mFrameTracker.setFrameReadyFence(frameReadyFence);
+        } else {
+            // There was no fence for this frame, so assume that it was ready
+            // to be presented at the desired present time.
+            mFrameTracker.setFrameReadyTime(desiredPresentTime);
+        }
+
         const HWComposer& hwc = mFlinger->getHwComposer();
-        const size_t offset = mFrameLatencyOffset;
-        mFrameStats[offset].timestamp = mSurfaceTexture->getTimestamp();
-        mFrameStats[offset].set = systemTime();
-        mFrameStats[offset].vsync = hwc.getRefreshTimestamp(HWC_DISPLAY_PRIMARY);
-        mFrameLatencyOffset = (mFrameLatencyOffset + 1) % 128;
+        sp<Fence> presentFence = hwc.getDisplayFence(HWC_DISPLAY_PRIMARY);
+        if (presentFence != NULL) {
+            mFrameTracker.setActualPresentFence(presentFence);
+        } else {
+            // The HWC doesn't support present fences, so use the refresh
+            // timestamp instead.
+            nsecs_t presentTime = hwc.getRefreshTimestamp(HWC_DISPLAY_PRIMARY);
+            mFrameTracker.setActualPresentTime(presentTime);
+        }
+
+        mFrameTracker.advanceFrame();
         mFrameLatencyNeeded = false;
     }
 }
@@ -721,27 +738,16 @@ void Layer::dump(String8& result, char* buffer, size_t SIZE) const
 void Layer::dumpStats(String8& result, char* buffer, size_t SIZE) const
 {
     LayerBaseClient::dumpStats(result, buffer, SIZE);
-    const size_t o = mFrameLatencyOffset;
     const nsecs_t period =
             mFlinger->getHwComposer().getRefreshPeriod(HWC_DISPLAY_PRIMARY);
     result.appendFormat("%lld\n", period);
-    for (size_t i=0 ; i<128 ; i++) {
-        const size_t index = (o+i) % 128;
-        const nsecs_t time_app   = mFrameStats[index].timestamp;
-        const nsecs_t time_set   = mFrameStats[index].set;
-        const nsecs_t time_vsync = mFrameStats[index].vsync;
-        result.appendFormat("%lld\t%lld\t%lld\n",
-                time_app,
-                time_vsync,
-                time_set);
-    }
-    result.append("\n");
+    mFrameTracker.dump(result);
 }
 
 void Layer::clearStats()
 {
     LayerBaseClient::clearStats();
-    memset(mFrameStats, 0, sizeof(mFrameStats));
+    mFrameTracker.clear();
 }
 
 uint32_t Layer::getEffectiveUsage(uint32_t usage) const

services/surfaceflinger/Layer.h

@@ -34,6 +34,7 @@
 #include <GLES/gl.h>
 #include <GLES/glext.h>
 
+#include "FrameTracker.h"
 #include "LayerBase.h"
 #include "SurfaceTextureLayer.h"
 #include "Transform.h"
@@ -129,17 +130,7 @@ private:
     bool mCurrentOpacity;
     bool mRefreshPending;
     bool mFrameLatencyNeeded;
-    int mFrameLatencyOffset;
-
-    struct Statistics {
-        Statistics() : timestamp(0), set(0), vsync(0) { }
-        nsecs_t timestamp;  // buffer timestamp
-        nsecs_t set;        // buffer displayed timestamp
-        nsecs_t vsync;      // vsync immediately before set
-    };
-
-    // protected by mLock
-    Statistics mFrameStats[128];
+    FrameTracker mFrameTracker;
 
     // constants
     PixelFormat mFormat;