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 #pragma once
18 
19 #include <ui/FenceTime.h>
20 #include <utils/Mutex.h>
21 #include <utils/RefBase.h>
22 #include <utils/Timers.h>
23 
24 #include <cstddef>
25 #include <string_view>
26 
27 namespace android {
28 
29 // FrameTracker tracks information about the most recently rendered frames. It
30 // uses a circular buffer of frame records, and is *NOT* thread-safe -
31 // mutexing must be done at a higher level if multi-threaded access is
32 // possible.
33 //
34 // Some of the time values tracked may be set either as a specific timestamp
35 // or a fence.  When a non-nullptr fence is set for a given time value, the
36 // signal time of that fence is used instead of the timestamp.
37 class FrameTracker {
38 
39 public:
40     // NUM_FRAME_RECORDS is the size of the circular buffer used to track the
41     // frame time history.
42     enum { NUM_FRAME_RECORDS = 128 };
43 
44     enum { NUM_FRAME_BUCKETS = 7 };
45 
46     FrameTracker();
47 
48     // setDesiredPresentTime sets the time at which the current frame
49     // should be presented to the user under ideal (i.e. zero latency)
50     // conditions.
51     void setDesiredPresentTime(nsecs_t desiredPresentTime);
52 
53     // setFrameReadyTime sets the time at which the current frame became ready
54     // to be presented to the user.  For example, if the frame contents is
55     // being written to memory by some asynchronous hardware, this would be
56     // the time at which those writes completed.
57     void setFrameReadyTime(nsecs_t readyTime);
58 
59     // setFrameReadyFence sets the fence that is used to get the time at which
60     // the current frame became ready to be presented to the user.
61     void setFrameReadyFence(std::shared_ptr<FenceTime>&& readyFence);
62 
63     // setActualPresentTime sets the timestamp at which the current frame became
64     // visible to the user.
65     void setActualPresentTime(nsecs_t displayTime);
66 
67     // setActualPresentFence sets the fence that is used to get the time
68     // at which the current frame became visible to the user.
69     void setActualPresentFence(std::shared_ptr<FenceTime>&& fence);
70 
71     // setDisplayRefreshPeriod sets the display refresh period in nanoseconds.
72     // This is used to compute frame presentation duration statistics relative
73     // to this period.
74     void setDisplayRefreshPeriod(nsecs_t displayPeriod);
75 
76     // advanceFrame advances the frame tracker to the next frame.
77     void advanceFrame();
78 
79     // clearStats clears the tracked frame stats.
80     void clearStats();
81 
82     // getStats gets the tracked frame stats.
83     void getStats(FrameStats* outStats) const;
84 
85     // logAndResetStats dumps the current statistics to the binary event log
86     // and then resets the accumulated statistics to their initial values.
87     void logAndResetStats(const std::string_view& name);
88 
89     // dumpStats dump appends the current frame display time history to the result string.
90     void dumpStats(std::string& result) const;
91 
92 private:
93     struct FrameRecord {
FrameRecordFrameRecord94         FrameRecord() :
95             desiredPresentTime(0),
96             frameReadyTime(0),
97             actualPresentTime(0) {}
98         nsecs_t desiredPresentTime;
99         nsecs_t frameReadyTime;
100         nsecs_t actualPresentTime;
101         std::shared_ptr<FenceTime> frameReadyFence;
102         std::shared_ptr<FenceTime> actualPresentFence;
103     };
104 
105     // processFences iterates over all the frame records that have a fence set
106     // and replaces that fence with a timestamp if the fence has signaled.  If
107     // the fence is not signaled the record's displayTime is set to INT64_MAX.
108     //
109     // This method is const because although it modifies the frame records it
110     // does so in such a way that the information represented should not
111     // change.  This allows it to be called from the dump method.
112     void processFencesLocked() const;
113 
114     // updateStatsLocked updates the running statistics that are gathered
115     // about the frame times.
116     void updateStatsLocked(size_t newFrameIdx) const;
117 
118     // resetFrameCounteresLocked sets all elements of the mNumFrames array to
119     // 0.
120     void resetFrameCountersLocked();
121 
122     // logStatsLocked dumps the current statistics to the binary event log.
123     void logStatsLocked(const std::string_view& name) const;
124 
125     // isFrameValidLocked returns true if the data for the given frame index is
126     // valid and has all arrived (i.e. there are no oustanding fences).
127     bool isFrameValidLocked(size_t idx) const;
128 
129     // mFrameRecords is the circular buffer storing the tracked data for each
130     // frame.
131     FrameRecord mFrameRecords[NUM_FRAME_RECORDS];
132 
133     // mOffset is the offset into mFrameRecords of the current frame.
134     size_t mOffset;
135 
136     // mNumFences is the total number of fences set in the frame records.  It
137     // is incremented each time a fence is added and decremented each time a
138     // signaled fence is removed in processFences or if advanceFrame clobbers
139     // a fence.
140     //
141     // The number of fences is tracked so that the run time of processFences
142     // doesn't grow with NUM_FRAME_RECORDS.
143     int mNumFences;
144 
145     // mNumFrames keeps a count of the number of frames with a duration in a
146     // particular range of vsync periods.  Element n of the array stores the
147     // number of frames with duration in the half-inclusive range
148     // [2^n, 2^(n+1)).  The last element of the array contains the count for
149     // all frames with duration greater than 2^(NUM_FRAME_BUCKETS-1).
150     int32_t mNumFrames[NUM_FRAME_BUCKETS];
151 
152     // mDisplayPeriod is the display refresh period of the display for which
153     // this FrameTracker is gathering information.
154     nsecs_t mDisplayPeriod;
155 
156     // mMutex is used to protect access to all member variables.
157     mutable Mutex mMutex;
158 };
159 
160 } // namespace android
161