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 <ui/FenceTime.h>
21 
22 #include <stddef.h>
23 
24 #include <utils/Mutex.h>
25 #include <utils/Timers.h>
26 #include <utils/RefBase.h>
27 
28 namespace android {
29 
30 class String8;
31 
32 // FrameTracker tracks information about the most recently rendered frames. It
33 // uses a circular buffer of frame records, and is *NOT* thread-safe -
34 // mutexing must be done at a higher level if multi-threaded access is
35 // possible.
36 //
37 // Some of the time values tracked may be set either as a specific timestamp
38 // or a fence.  When a non-nullptr fence is set for a given time value, the
39 // signal time of that fence is used instead of the timestamp.
40 class FrameTracker {
41 
42 public:
43     // NUM_FRAME_RECORDS is the size of the circular buffer used to track the
44     // frame time history.
45     enum { NUM_FRAME_RECORDS = 128 };
46 
47     enum { NUM_FRAME_BUCKETS = 7 };
48 
49     FrameTracker();
50 
51     // setDesiredPresentTime sets the time at which the current frame
52     // should be presented to the user under ideal (i.e. zero latency)
53     // conditions.
54     void setDesiredPresentTime(nsecs_t desiredPresentTime);
55 
56     // setFrameReadyTime sets the time at which the current frame became ready
57     // to be presented to the user.  For example, if the frame contents is
58     // being written to memory by some asynchronous hardware, this would be
59     // the time at which those writes completed.
60     void setFrameReadyTime(nsecs_t readyTime);
61 
62     // setFrameReadyFence sets the fence that is used to get the time at which
63     // the current frame became ready to be presented to the user.
64     void setFrameReadyFence(std::shared_ptr<FenceTime>&& readyFence);
65 
66     // setActualPresentTime sets the timestamp at which the current frame became
67     // visible to the user.
68     void setActualPresentTime(nsecs_t displayTime);
69 
70     // setActualPresentFence sets the fence that is used to get the time
71     // at which the current frame became visible to the user.
72     void setActualPresentFence(std::shared_ptr<FenceTime>&& fence);
73 
74     // setDisplayRefreshPeriod sets the display refresh period in nanoseconds.
75     // This is used to compute frame presentation duration statistics relative
76     // to this period.
77     void setDisplayRefreshPeriod(nsecs_t displayPeriod);
78 
79     // advanceFrame advances the frame tracker to the next frame.
80     void advanceFrame();
81 
82     // clearStats clears the tracked frame stats.
83     void clearStats();
84 
85     // getStats gets the tracked frame stats.
86     void getStats(FrameStats* outStats) const;
87 
88     // logAndResetStats dumps the current statistics to the binary event log
89     // and then resets the accumulated statistics to their initial values.
90     void logAndResetStats(const String8& name);
91 
92     // dumpStats dump appends the current frame display time history to the result string.
93     void dumpStats(std::string& result) const;
94 
95 private:
96     struct FrameRecord {
FrameRecordFrameRecord97         FrameRecord() :
98             desiredPresentTime(0),
99             frameReadyTime(0),
100             actualPresentTime(0) {}
101         nsecs_t desiredPresentTime;
102         nsecs_t frameReadyTime;
103         nsecs_t actualPresentTime;
104         std::shared_ptr<FenceTime> frameReadyFence;
105         std::shared_ptr<FenceTime> actualPresentFence;
106     };
107 
108     // processFences iterates over all the frame records that have a fence set
109     // and replaces that fence with a timestamp if the fence has signaled.  If
110     // the fence is not signaled the record's displayTime is set to INT64_MAX.
111     //
112     // This method is const because although it modifies the frame records it
113     // does so in such a way that the information represented should not
114     // change.  This allows it to be called from the dump method.
115     void processFencesLocked() const;
116 
117     // updateStatsLocked updates the running statistics that are gathered
118     // about the frame times.
119     void updateStatsLocked(size_t newFrameIdx) const;
120 
121     // resetFrameCounteresLocked sets all elements of the mNumFrames array to
122     // 0.
123     void resetFrameCountersLocked();
124 
125     // logStatsLocked dumps the current statistics to the binary event log.
126     void logStatsLocked(const String8& name) const;
127 
128     // isFrameValidLocked returns true if the data for the given frame index is
129     // valid and has all arrived (i.e. there are no oustanding fences).
130     bool isFrameValidLocked(size_t idx) const;
131 
132     // mFrameRecords is the circular buffer storing the tracked data for each
133     // frame.
134     FrameRecord mFrameRecords[NUM_FRAME_RECORDS];
135 
136     // mOffset is the offset into mFrameRecords of the current frame.
137     size_t mOffset;
138 
139     // mNumFences is the total number of fences set in the frame records.  It
140     // is incremented each time a fence is added and decremented each time a
141     // signaled fence is removed in processFences or if advanceFrame clobbers
142     // a fence.
143     //
144     // The number of fences is tracked so that the run time of processFences
145     // doesn't grow with NUM_FRAME_RECORDS.
146     int mNumFences;
147 
148     // mNumFrames keeps a count of the number of frames with a duration in a
149     // particular range of vsync periods.  Element n of the array stores the
150     // number of frames with duration in the half-inclusive range
151     // [2^n, 2^(n+1)).  The last element of the array contains the count for
152     // all frames with duration greater than 2^(NUM_FRAME_BUCKETS-1).
153     int32_t mNumFrames[NUM_FRAME_BUCKETS];
154 
155     // mDisplayPeriod is the display refresh period of the display for which
156     // this FrameTracker is gathering information.
157     nsecs_t mDisplayPeriod;
158 
159     // mMutex is used to protect access to all member variables.
160     mutable Mutex mMutex;
161 };
162 
163 }
164 
165 #endif // ANDROID_FRAMETRACKER_H
166