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    // clear resets all the tracked frame data to zero.
82    void clear();
83
84    // logAndResetStats dumps the current statistics to the binary event log
85    // and then resets the accumulated statistics to their initial values.
86    void logAndResetStats(const String8& name);
87
88    // dump appends the current frame display time history to the result string.
89    void dump(String8& result) const;
90
91private:
92    struct FrameRecord {
93        FrameRecord() :
94            desiredPresentTime(0),
95            frameReadyTime(0),
96            actualPresentTime(0) {}
97        nsecs_t desiredPresentTime;
98        nsecs_t frameReadyTime;
99        nsecs_t actualPresentTime;
100        sp<Fence> frameReadyFence;
101        sp<Fence> actualPresentFence;
102    };
103
104    // processFences iterates over all the frame records that have a fence set
105    // and replaces that fence with a timestamp if the fence has signaled.  If
106    // the fence is not signaled the record's displayTime is set to INT64_MAX.
107    //
108    // This method is const because although it modifies the frame records it
109    // does so in such a way that the information represented should not
110    // change.  This allows it to be called from the dump method.
111    void processFencesLocked() const;
112
113    // updateStatsLocked updates the running statistics that are gathered
114    // about the frame times.
115    void updateStatsLocked(size_t newFrameIdx) const;
116
117    // resetFrameCounteresLocked sets all elements of the mNumFrames array to
118    // 0.
119    void resetFrameCountersLocked();
120
121    // logStatsLocked dumps the current statistics to the binary event log.
122    void logStatsLocked(const String8& name) const;
123
124    // isFrameValidLocked returns true if the data for the given frame index is
125    // valid and has all arrived (i.e. there are no oustanding fences).
126    bool isFrameValidLocked(size_t idx) const;
127
128    // mFrameRecords is the circular buffer storing the tracked data for each
129    // frame.
130    FrameRecord mFrameRecords[NUM_FRAME_RECORDS];
131
132    // mOffset is the offset into mFrameRecords of the current frame.
133    size_t mOffset;
134
135    // mNumFences is the total number of fences set in the frame records.  It
136    // is incremented each time a fence is added and decremented each time a
137    // signaled fence is removed in processFences or if advanceFrame clobbers
138    // a fence.
139    //
140    // The number of fences is tracked so that the run time of processFences
141    // doesn't grow with NUM_FRAME_RECORDS.
142    int mNumFences;
143
144    // mNumFrames keeps a count of the number of frames with a duration in a
145    // particular range of vsync periods.  Element n of the array stores the
146    // number of frames with duration in the half-inclusive range
147    // [2^n, 2^(n+1)).  The last element of the array contains the count for
148    // all frames with duration greater than 2^(NUM_FRAME_BUCKETS-1).
149    int32_t mNumFrames[NUM_FRAME_BUCKETS];
150
151    // mDisplayPeriod is the display refresh period of the display for which
152    // this FrameTracker is gathering information.
153    nsecs_t mDisplayPeriod;
154
155    // mMutex is used to protect access to all member variables.
156    mutable Mutex mMutex;
157};
158
159}
160
161#endif // ANDROID_FRAMETRACKER_H
162