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
diff --git a/services/surfaceflinger/FrameTracker.h b/services/surfaceflinger/FrameTracker.h
new file mode 100644
index 0000000..e8a8c48
--- /dev/null
+++ b/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