FastMixer.h revision ee499291404a192b059f2e04c5afc65aa6cdd74c 
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_AUDIO_FAST_MIXER_H
18#define ANDROID_AUDIO_FAST_MIXER_H
19
20#include <linux/futex.h>
21#include <sys/syscall.h>
22#include <utils/Debug.h>
23#include <utils/Thread.h>
24#include "StateQueue.h"
25#include "FastMixerState.h"
26
27namespace android {
28
29typedef StateQueue<FastMixerState> FastMixerStateQueue;
30
31class FastMixer : public Thread {
32
33public:
34            FastMixer() : Thread(false /*canCallJava*/) { }
35    virtual ~FastMixer() { }
36
37            FastMixerStateQueue* sq() { return &mSQ; }
38
39private:
40    virtual bool                threadLoop();
41            FastMixerStateQueue mSQ;
42
43};  // class FastMixer
44
45// Describes the underrun status for a single "pull" attempt
46enum FastTrackUnderrunStatus {
47    UNDERRUN_FULL,      // framesReady() is full frame count, no underrun
48    UNDERRUN_PARTIAL,   // framesReady() is non-zero but < full frame count, partial underrun
49    UNDERRUN_EMPTY,     // framesReady() is zero, total underrun
50};
51
52// Underrun counters are not reset to zero for new tracks or if track generation changes.
53// This packed representation is used to keep the information atomic.
54union FastTrackUnderruns {
55    FastTrackUnderruns() { mAtomic = 0;
56            COMPILE_TIME_ASSERT_FUNCTION_SCOPE(sizeof(FastTrackUnderruns) == sizeof(uint32_t)); }
57    FastTrackUnderruns(const FastTrackUnderruns& copyFrom) : mAtomic(copyFrom.mAtomic) { }
58    FastTrackUnderruns& operator=(const FastTrackUnderruns& rhs)
59            { if (this != &rhs) mAtomic = rhs.mAtomic; return *this; }
60    struct {
61#define UNDERRUN_BITS 10
62#define UNDERRUN_MASK ((1 << UNDERRUN_BITS) - 1)
63        uint32_t mFull    : UNDERRUN_BITS; // framesReady() is full frame count
64        uint32_t mPartial : UNDERRUN_BITS; // framesReady() is non-zero but < full frame count
65        uint32_t mEmpty   : UNDERRUN_BITS; // framesReady() is zero
66        FastTrackUnderrunStatus mMostRecent : 2;    // status of most recent framesReady()
67    }        mBitFields;
68private:
69    uint32_t mAtomic;
70};
71
72// Represents the dump state of a fast track
73struct FastTrackDump {
74    FastTrackDump() : mFramesReady(0) { }
75    /*virtual*/ ~FastTrackDump() { }
76    FastTrackUnderruns mUnderruns;
77    size_t mFramesReady;        // most recent value only; no long-term statistics kept
78};
79
80// The FastMixerDumpState keeps a cache of FastMixer statistics that can be logged by dumpsys.
81// Each individual native word-sized field is accessed atomically.  But the
82// overall structure is non-atomic, that is there may be an inconsistency between fields.
83// No barriers or locks are used for either writing or reading.
84// Only POD types are permitted, and the contents shouldn't be trusted (i.e. do range checks).
85// It has a different lifetime than the FastMixer, and so it can't be a member of FastMixer.
86struct FastMixerDumpState {
87    FastMixerDumpState(
88#ifdef FAST_MIXER_STATISTICS
89            uint32_t samplingN = kSamplingNforLowRamDevice
90#endif
91            );
92    /*virtual*/ ~FastMixerDumpState();
93
94    void dump(int fd) const;    // should only be called on a stable copy, not the original
95
96    FastMixerState::Command mCommand;   // current command
97    uint32_t mWriteSequence;    // incremented before and after each write()
98    uint32_t mFramesWritten;    // total number of frames written successfully
99    uint32_t mNumTracks;        // total number of active fast tracks
100    uint32_t mWriteErrors;      // total number of write() errors
101    uint32_t mUnderruns;        // total number of underruns
102    uint32_t mOverruns;         // total number of overruns
103    uint32_t mSampleRate;
104    size_t   mFrameCount;
105    struct timespec mMeasuredWarmupTs;  // measured warmup time
106    uint32_t mWarmupCycles;     // number of loop cycles required to warmup
107    uint32_t mTrackMask;        // mask of active tracks
108    FastTrackDump   mTracks[FastMixerState::kMaxFastTracks];
109
110#ifdef FAST_MIXER_STATISTICS
111    // Recently collected samples of per-cycle monotonic time, thread CPU time, and CPU frequency.
112    // kSamplingN is max size of sampling frame (statistics), and must be a power of 2 <= 0x8000.
113    // The sample arrays are virtually allocated based on this compile-time constant,
114    // but are only initialized and used based on the runtime parameter mSamplingN.
115    static const uint32_t kSamplingN = 0x8000;
116    // Compile-time constant for a "low RAM device", must be a power of 2 <= kSamplingN.
117    // This value was chosen such that each array uses 1 small page (4 Kbytes).
118    static const uint32_t kSamplingNforLowRamDevice = 0x400;
119    // Corresponding runtime maximum size of sample arrays, must be a power of 2 <= kSamplingN.
120    uint32_t mSamplingN;
121    // The bounds define the interval of valid samples, and are represented as follows:
122    //      newest open (excluded) endpoint   = lower 16 bits of bounds, modulo N
123    //      oldest closed (included) endpoint = upper 16 bits of bounds, modulo N
124    // Number of valid samples is newest - oldest.
125    uint32_t mBounds;                   // bounds for mMonotonicNs, mThreadCpuNs, and mCpukHz
126    // The elements in the *Ns arrays are in units of nanoseconds <= 3999999999.
127    uint32_t mMonotonicNs[kSamplingN];  // delta monotonic (wall clock) time
128    uint32_t mLoadNs[kSamplingN];       // delta CPU load in time
129#ifdef CPU_FREQUENCY_STATISTICS
130    uint32_t mCpukHz[kSamplingN];       // absolute CPU clock frequency in kHz, bits 0-3 are CPU#
131#endif
132    // Increase sampling window after construction, must be a power of 2 <= kSamplingN
133    void    increaseSamplingN(uint32_t samplingN);
134#endif
135};
136
137}   // namespace android
138
139#endif  // ANDROID_AUDIO_FAST_MIXER_H
140