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* 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
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
#include <stddef.h>
#include <utils/Mutex.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 {
// NUM_FRAME_RECORDS is the size of the circular buffer used to track the
// frame time history.
enum { NUM_FRAME_RECORDS = 128 };
// 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;
struct FrameRecord {
FrameRecord() :
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 processFencesLocked() 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;
// mMutex is used to protect access to all member variables.
mutable Mutex mMutex;