Merge "CPU statistics library"

/*

 * Copyright (C) 2011 The Android Open Source Project

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at

 *

 *      http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

#ifndef _CENTRAL_TENDENCY_STATISTICS_H

#define _CENTRAL_TENDENCY_STATISTICS_H

#include <math.h>

// Not multithread safe

class CentralTendencyStatistics {

public:

    CentralTendencyStatistics() :

            mMean(NAN), mMedian(NAN), mMinimum(INFINITY), mMaximum(-INFINITY), mN(0), mM2(0),

            mVariance(NAN), mVarianceKnownForN(0), mStddev(NAN), mStddevKnownForN(0) { }

    ~CentralTendencyStatistics() { }

    // add x to the set of samples

    void sample(double x);

    // return the arithmetic mean of all samples so far

    double mean() const { return mMean; }

    // return the minimum of all samples so far

    double minimum() const { return mMinimum; }

    // return the maximum of all samples so far

    double maximum() const { return mMaximum; }

    // return the variance of all samples so far

    double variance() const;

    // return the standard deviation of all samples so far

    double stddev() const;

    // return the number of samples added so far

    unsigned n() const { return mN; }

    // reset the set of samples to be empty

    void reset();

private:

    double mMean;

    double mMedian;

    double mMinimum;

    double mMaximum;

    unsigned mN;    // number of samples so far

    double mM2;

    // cached variance, and n at time of caching

    mutable double mVariance;

    mutable unsigned mVarianceKnownForN;

    // cached standard deviation, and n at time of caching

    mutable double mStddev;

    mutable unsigned mStddevKnownForN;

};

#endif // _CENTRAL_TENDENCY_STATISTICS_H

This is a static library of CPU usage statistics, originally written

for audio but most are not actually specific to audio.

Requirements to be here:

 * should be related to CPU usage statistics

 * should be portable to host; avoid Android OS dependencies without a conditional

/*

 * Copyright (C) 2011 The Android Open Source Project

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at

 *

 *      http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

#ifndef _THREAD_CPU_USAGE_H

#define _THREAD_CPU_USAGE_H

#include <cpustats/CentralTendencyStatistics.h>

// Track CPU usage for the current thread, and maintain statistics on

// the CPU usage.  Units are in per-thread CPU ns, as reported by

// clock_gettime(CLOCK_THREAD_CPUTIME_ID).  Simple usage: for cyclic

// threads where you want to measure the execution time of the whole

// cycle, just call sampleAndEnable() at the start of each cycle.

// Then call statistics() to get the results, and resetStatistics()

// to start a new set of measurements.

// For acyclic threads, or for cyclic threads where you want to measure

// only part of each cycle, call enable(), disable(), and/or setEnabled()

// to demarcate the region(s) of interest, and then call sample() periodically.

// This class is not thread-safe for concurrent calls from multiple threads;

// the methods of this class may only be called by the current thread

// which constructed the object.

class ThreadCpuUsage

{

public:

    ThreadCpuUsage() :

        mIsEnabled(false),

        mWasEverEnabled(false),

        mAccumulator(0),

        // mPreviousTs

        // mMonotonicTs

        mMonotonicKnown(false)

        // mStatistics

        { }

    ~ThreadCpuUsage() { }

    // Return whether currently tracking CPU usage by current thread

    bool isEnabled()    { return mIsEnabled; }

    // Enable tracking of CPU usage by current thread;

    // any CPU used from this point forward will be tracked.

    // Returns the previous enabled status.

    bool enable()       { return setEnabled(true); }

    // Disable tracking of CPU usage by current thread;

    // any CPU used from this point forward will be ignored.

    // Returns the previous enabled status.

    bool disable()      { return setEnabled(false); }

    // Set the enabled status and return the previous enabled status.

    // This method is intended to be used for safe nested enable/disabling.

    bool setEnabled(bool isEnabled);

    // Add a sample point for central tendency statistics, and also

    // enable tracking if needed.  If tracking has never been enabled, then

    // enables tracking but does not add a sample (it is not possible to add

    // a sample the first time because no previous).  Otherwise if tracking is

    // enabled, then adds a sample for tracked CPU ns since the previous

    // sample, or since the first call to sampleAndEnable(), enable(), or

    // setEnabled(true).  If there was a previous sample but tracking is

    // now disabled, then adds a sample for the tracked CPU ns accumulated

    // up until the most recent disable(), resets this accumulator, and then

    // enables tracking.  Calling this method rather than enable() followed

    // by sample() avoids a race condition for the first sample.

    void sampleAndEnable();

    // Add a sample point for central tendency statistics, but do not

    // change the tracking enabled status.  If tracking has either never been

    // enabled, or has never been enabled since the last sample, then log a warning

    // and don't add sample.  Otherwise, adds a sample for tracked CPU ns since

    // the previous sample or since the first call to sampleAndEnable(),

    // enable(), or setEnabled(true) if no previous sample.

    void sample();

    // Return the elapsed delta wall clock ns since initial enable or statistics reset,

    // as reported by clock_gettime(CLOCK_MONOTONIC).

    long long elapsed() const;

    // Reset statistics and elapsed.  Has no effect on tracking or accumulator.

    void resetStatistics();

    // Return a const reference to the central tendency statistics.

    // Note that only the const methods can be called on this object.

    const CentralTendencyStatistics& statistics() const {

        return mStatistics;

    }

private:

    bool mIsEnabled;                // whether tracking is currently enabled

    bool mWasEverEnabled;           // whether tracking was ever enabled

    long long mAccumulator;         // accumulated thread CPU time since last sample, in ns

    struct timespec mPreviousTs;    // most recent thread CPU time, valid only if mIsEnabled is true

    struct timespec mMonotonicTs;   // most recent monotonic time

    bool mMonotonicKnown;           // whether mMonotonicTs has been set

    CentralTendencyStatistics mStatistics;

};

#endif //  _THREAD_CPU_USAGE_H

LOCAL_PATH:= $(call my-dir)

include $(CLEAR_VARS)

LOCAL_SRC_FILES :=     \

        CentralTendencyStatistics.cpp \

        ThreadCpuUsage.cpp

LOCAL_MODULE := libcpustats

include $(BUILD_STATIC_LIBRARY)

include $(CLEAR_VARS)

LOCAL_SRC_FILES :=     \

        CentralTendencyStatistics.cpp \

        ThreadCpuUsage.cpp

LOCAL_MODULE := libcpustats

include $(BUILD_HOST_STATIC_LIBRARY)

/*

 * Copyright (C) 2011 The Android Open Source Project

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at

 *

 *      http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

#include <stdlib.h>

#include <cpustats/CentralTendencyStatistics.h>

void CentralTendencyStatistics::sample(double x)

{

    // update min and max

    if (x < mMinimum)

        mMinimum = x;

    if (x > mMaximum)

        mMaximum = x;

    // Knuth

    if (mN == 0) {

        mMean = 0;

    }

    ++mN;

    double delta = x - mMean;

    mMean += delta / mN;

    mM2 += delta * (x - mMean);

}

void CentralTendencyStatistics::reset()

{

    mMean = NAN;

    mMedian = NAN;

    mMinimum = INFINITY;

    mMaximum = -INFINITY;

    mN = 0;

    mM2 = 0;

    mVariance = NAN;

    mVarianceKnownForN = 0;

    mStddev = NAN;

    mStddevKnownForN = 0;

}

double CentralTendencyStatistics::variance() const

{

    double variance;

    if (mVarianceKnownForN != mN) {

        if (mN > 1) {

            // double variance_n = M2/n;

            variance = mM2 / (mN - 1);

        } else {

            variance = NAN;

        }

        mVariance = variance;

        mVarianceKnownForN = mN;

    } else {

        variance = mVariance;

    }

    return variance;

}

double CentralTendencyStatistics::stddev() const

{

    double stddev;

    if (mStddevKnownForN != mN) {

        stddev = sqrt(variance());

        mStddev = stddev;

        mStddevKnownForN = mN;

    } else {

        stddev = mStddev;

    }

    return stddev;

}