1/*
2 * Copyright (C) 2012 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef ANDROID_FRAMETRACKER_H
18#define ANDROID_FRAMETRACKER_H
19
20#include <stddef.h>
21
22#include <utils/Mutex.h>
23#include <utils/Timers.h>
24#include <utils/RefBase.h>
25
26namespace android {
27
28class String8;
29class Fence;
30
31// FrameTracker tracks information about the most recently rendered frames. It
32// uses a circular buffer of frame records, and is *NOT* thread-safe -
33// mutexing must be done at a higher level if multi-threaded access is
34// possible.
35//
36// Some of the time values tracked may be set either as a specific timestamp
37// or a fence.  When a non-NULL fence is set for a given time value, the
38// signal time of that fence is used instead of the timestamp.
39class FrameTracker {
40
41public:
42    // NUM_FRAME_RECORDS is the size of the circular buffer used to track the
43    // frame time history.
44    enum { NUM_FRAME_RECORDS = 128 };
45
46    enum { NUM_FRAME_BUCKETS = 7 };
47
48    FrameTracker();
49
50    // setDesiredPresentTime sets the time at which the current frame
51    // should be presented to the user under ideal (i.e. zero latency)
52    // conditions.
53    void setDesiredPresentTime(nsecs_t desiredPresentTime);
54
55    // setFrameReadyTime sets the time at which the current frame became ready
56    // to be presented to the user.  For example, if the frame contents is
57    // being written to memory by some asynchronous hardware, this would be
58    // the time at which those writes completed.
59    void setFrameReadyTime(nsecs_t readyTime);
60
61    // setFrameReadyFence sets the fence that is used to get the time at which
62    // the current frame became ready to be presented to the user.
63    void setFrameReadyFence(const sp<Fence>& readyFence);
64
65    // setActualPresentTime sets the timestamp at which the current frame became
66    // visible to the user.
67    void setActualPresentTime(nsecs_t displayTime);
68
69    // setActualPresentFence sets the fence that is used to get the time
70    // at which the current frame became visible to the user.
71    void setActualPresentFence(const sp<Fence>& fence);
72
73    // setDisplayRefreshPeriod sets the display refresh period in nanoseconds.
74    // This is used to compute frame presentation duration statistics relative
75    // to this period.
76    void setDisplayRefreshPeriod(nsecs_t displayPeriod);
77
78    // advanceFrame advances the frame tracker to the next frame.
79    void advanceFrame();
80
81    // clearStats clears the tracked frame stats.
82    void clearStats();
83
84    // getStats gets the tracked frame stats.
85    void getStats(FrameStats* outStats) const;
86
87    // logAndResetStats dumps the current statistics to the binary event log
88    // and then resets the accumulated statistics to their initial values.
89    void logAndResetStats(const String8& name);
90
91    // dumpStats dump appends the current frame display time history to the result string.
92    void dumpStats(String8& result) const;
93
94private:
95    struct FrameRecord {
96        FrameRecord() :
97            desiredPresentTime(0),
98            frameReadyTime(0),
99            actualPresentTime(0) {}
100        nsecs_t desiredPresentTime;
101        nsecs_t frameReadyTime;
102        nsecs_t actualPresentTime;
103        sp<Fence> frameReadyFence;
104        sp<Fence> actualPresentFence;
105    };
106
107    // processFences iterates over all the frame records that have a fence set
108    // and replaces that fence with a timestamp if the fence has signaled.  If
109    // the fence is not signaled the record's displayTime is set to INT64_MAX.
110    //
111    // This method is const because although it modifies the frame records it
112    // does so in such a way that the information represented should not
113    // change.  This allows it to be called from the dump method.
114    void processFencesLocked() const;
115
116    // updateStatsLocked updates the running statistics that are gathered
117    // about the frame times.
118    void updateStatsLocked(size_t newFrameIdx) const;
119
120    // resetFrameCounteresLocked sets all elements of the mNumFrames array to
121    // 0.
122    void resetFrameCountersLocked();
123
124    // logStatsLocked dumps the current statistics to the binary event log.
125    void logStatsLocked(const String8& name) const;
126
127    // isFrameValidLocked returns true if the data for the given frame index is
128    // valid and has all arrived (i.e. there are no oustanding fences).
129    bool isFrameValidLocked(size_t idx) const;
130
131    // mFrameRecords is the circular buffer storing the tracked data for each
132    // frame.
133    FrameRecord mFrameRecords[NUM_FRAME_RECORDS];
134
135    // mOffset is the offset into mFrameRecords of the current frame.
136    size_t mOffset;
137
138    // mNumFences is the total number of fences set in the frame records.  It
139    // is incremented each time a fence is added and decremented each time a
140    // signaled fence is removed in processFences or if advanceFrame clobbers
141    // a fence.
142    //
143    // The number of fences is tracked so that the run time of processFences
144    // doesn't grow with NUM_FRAME_RECORDS.
145    int mNumFences;
146
147    // mNumFrames keeps a count of the number of frames with a duration in a
148    // particular range of vsync periods.  Element n of the array stores the
149    // number of frames with duration in the half-inclusive range
150    // [2^n, 2^(n+1)).  The last element of the array contains the count for
151    // all frames with duration greater than 2^(NUM_FRAME_BUCKETS-1).
152    int32_t mNumFrames[NUM_FRAME_BUCKETS];
153
154    // mDisplayPeriod is the display refresh period of the display for which
155    // this FrameTracker is gathering information.
156    nsecs_t mDisplayPeriod;
157
158    // mMutex is used to protect access to all member variables.
159    mutable Mutex mMutex;
160};
161
162}
163
164#endif // ANDROID_FRAMETRACKER_H
165