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/*
* Copyright (C) 2017 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.
*/
#define LOG_TAG "PerformanceAnalysis"
// #define LOG_NDEBUG 0
// #define WRITE_TO_FILE
#include <algorithm>
#include <climits>
#include <deque>
#include <iomanip>
#include <math.h>
#include <numeric>
#include <sstream>
#include <string>
#include <vector>
#include <stdarg.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include <sys/prctl.h>
#include <time.h>
#include <new>
#include <audio_utils/LogPlot.h>
#include <audio_utils/roundup.h>
#include <media/nblog/NBLog.h>
#include <media/nblog/PerformanceAnalysis.h>
#include <media/nblog/ReportPerformance.h>
#include <utils/Log.h>
#include <utils/String8.h>
#include <utils/Timers.h>
#include <queue>
#include <utility>
namespace android {
namespace ReportPerformance {
void Histogram::add(double value)
{
if (mBinSize <= 0 || mBins.size() < 2) {
return;
}
// TODO Handle domain and range error exceptions?
const int unboundedIndex = lround((value - mLow) / mBinSize) + 1;
// std::clamp is introduced in C++17
//const int index = std::clamp(unboundedIndex, 0, (int)(mBins.size() - 1));
const int index = std::max(0, std::min((int)(mBins.size() - 1), unboundedIndex));
mBins[index]++;
mTotalCount++;
}
void Histogram::clear()
{
std::fill(mBins.begin(), mBins.end(), 0);
mTotalCount = 0;
}
uint64_t Histogram::totalCount() const
{
return mTotalCount;
}
std::string Histogram::toString() const {
std::stringstream ss;
static constexpr char kDivider = '|';
ss << kVersion << "," << mBinSize << "," << mNumBins << "," << mLow << ",{";
bool first = true;
for (size_t i = 0; i < mBins.size(); i++) {
if (mBins[i] != 0) {
if (!first) {
ss << ",";
}
ss << static_cast<int>(i) - 1 << kDivider << mBins[i];
first = false;
}
}
ss << "}";
return ss.str();
}
std::string Histogram::asciiArtString(size_t indent) const {
if (totalCount() == 0 || mBinSize <= 0 || mBins.size() < 2) {
return "";
}
static constexpr char kMarker = '-';
// One increment is considered one step of a bin's height.
static constexpr size_t kMarkersPerIncrement = 2;
static constexpr size_t kMaxIncrements = 64 + 1;
static constexpr size_t kMaxNumberWidth = 7;
static const std::string kMarkers(kMarkersPerIncrement * kMaxIncrements, kMarker);
static const std::string kSpaces(kMarkersPerIncrement * kMaxIncrements, ' ');
// get the last n characters of s, or the whole string if it is shorter
auto getTail = [](const size_t n, const std::string &s) {
return s.c_str() + s.size() - std::min(n, s.size());
};
// Since totalCount() > 0, mBins is not empty and maxCount > 0.
const unsigned maxCount = *std::max_element(mBins.begin(), mBins.end());
const size_t maxIncrements = log2(maxCount) + 1;
std::stringstream ss;
// Non-zero bins must exist at this point because totalCount() > 0.
size_t firstNonZeroBin = 0;
// If firstNonZeroBin reaches mBins.size() - 1, then it must be a nonzero bin.
for (; firstNonZeroBin < mBins.size() - 1 && mBins[firstNonZeroBin] == 0; firstNonZeroBin++) {}
const size_t firstBinToPrint = firstNonZeroBin == 0 ? 0 : firstNonZeroBin - 1;
size_t lastNonZeroBin = mBins.size() - 1;
// If lastNonZeroBin reaches 0, then it must be a nonzero bin.
for (; lastNonZeroBin > 0 && mBins[lastNonZeroBin] == 0; lastNonZeroBin--) {}
const size_t lastBinToPrint = lastNonZeroBin == mBins.size() - 1 ? lastNonZeroBin
: lastNonZeroBin + 1;
for (size_t bin = firstBinToPrint; bin <= lastBinToPrint; bin++) {
ss << std::setw(indent + kMaxNumberWidth);
if (bin == 0) {
ss << "<";
} else if (bin == mBins.size() - 1) {
ss << ">";
} else {
ss << mLow + (bin - 1) * mBinSize;
}
ss << " |";
size_t increments = 0;
const uint64_t binCount = mBins[bin];
if (binCount > 0) {
increments = log2(binCount) + 1;
ss << getTail(increments * kMarkersPerIncrement, kMarkers);
}
ss << getTail((maxIncrements - increments + 1) * kMarkersPerIncrement, kSpaces)
<< binCount << "\n";
}
ss << "\n";
return ss.str();
}
//------------------------------------------------------------------------------
// Given an audio processing wakeup timestamp, buckets the time interval
// since the previous timestamp into a histogram, searches for
// outliers, analyzes the outlier series for unexpectedly
// small or large values and stores these as peaks
void PerformanceAnalysis::logTsEntry(timestamp ts) {
// after a state change, start a new series and do not
// record time intervals in-between
if (mBufferPeriod.mPrevTs == 0) {
mBufferPeriod.mPrevTs = ts;
return;
}
// calculate time interval between current and previous timestamp
const msInterval diffMs = static_cast<msInterval>(
deltaMs(mBufferPeriod.mPrevTs, ts));
const int diffJiffy = deltaJiffy(mBufferPeriod.mPrevTs, ts);
// old versus new weight ratio when updating the buffer period mean
static constexpr double exponentialWeight = 0.999;
// update buffer period mean with exponential weighting
mBufferPeriod.mMean = (mBufferPeriod.mMean < 0) ? diffMs :
exponentialWeight * mBufferPeriod.mMean + (1.0 - exponentialWeight) * diffMs;
// set mOutlierFactor to a smaller value for the fastmixer thread
const int kFastMixerMax = 10;
// NormalMixer times vary much more than FastMixer times.
// TODO: mOutlierFactor values are set empirically based on what appears to be
// an outlier. Learn these values from the data.
mBufferPeriod.mOutlierFactor = mBufferPeriod.mMean < kFastMixerMax ? 1.8 : 2.0;
// set outlier threshold
mBufferPeriod.mOutlier = mBufferPeriod.mMean * mBufferPeriod.mOutlierFactor;
// Check whether the time interval between the current timestamp
// and the previous one is long enough to count as an outlier
const bool isOutlier = detectAndStoreOutlier(diffMs);
// If an outlier was found, check whether it was a peak
if (isOutlier) {
/*bool isPeak =*/ detectAndStorePeak(
mOutlierData[0].first, mOutlierData[0].second);
// TODO: decide whether to insert a new empty histogram if a peak
// TODO: remove isPeak if unused to avoid "unused variable" error
// occurred at the current timestamp
}
// Insert a histogram to mHists if it is empty, or
// close the current histogram and insert a new empty one if
// if the current histogram has spanned its maximum time interval.
if (mHists.empty() ||
deltaMs(mHists[0].first, ts) >= kMaxLength.HistTimespanMs) {
mHists.emplace_front(ts, std::map<int, int>());
// When memory is full, delete oldest histogram
// TODO: use a circular buffer
if (mHists.size() >= kMaxLength.Hists) {
mHists.resize(kMaxLength.Hists);
}
}
// add current time intervals to histogram
++mHists[0].second[diffJiffy];
// update previous timestamp
mBufferPeriod.mPrevTs = ts;
}
// forces short-term histogram storage to avoid adding idle audio time interval
// to buffer period data
void PerformanceAnalysis::handleStateChange() {
mBufferPeriod.mPrevTs = 0;
return;
}
// Checks whether the time interval between two outliers is far enough from
// a typical delta to be considered a peak.
// looks for changes in distribution (peaks), which can be either positive or negative.
// The function sets the mean to the starting value and sigma to 0, and updates
// them as long as no peak is detected. When a value is more than 'threshold'
// standard deviations from the mean, a peak is detected and the mean and sigma
// are set to the peak value and 0.
bool PerformanceAnalysis::detectAndStorePeak(msInterval diff, timestamp ts) {
bool isPeak = false;
if (mOutlierData.empty()) {
return false;
}
// Update mean of the distribution
// TypicalDiff is used to check whether a value is unusually large
// when we cannot use standard deviations from the mean because the sd is set to 0.
mOutlierDistribution.mTypicalDiff = (mOutlierDistribution.mTypicalDiff *
(mOutlierData.size() - 1) + diff) / mOutlierData.size();
// Initialize short-term mean at start of program
if (mOutlierDistribution.mMean == 0) {
mOutlierDistribution.mMean = diff;
}
// Update length of current sequence of outliers
mOutlierDistribution.mN++;
// Check whether a large deviation from the mean occurred.
// If the standard deviation has been reset to zero, the comparison is
// instead to the mean of the full mOutlierInterval sequence.
if ((fabs(diff - mOutlierDistribution.mMean) <
mOutlierDistribution.kMaxDeviation * mOutlierDistribution.mSd) ||
(mOutlierDistribution.mSd == 0 &&
fabs(diff - mOutlierDistribution.mMean) <
mOutlierDistribution.mTypicalDiff)) {
// update the mean and sd using online algorithm
// https://en.wikipedia.org/wiki/
// Algorithms_for_calculating_variance#Online_algorithm
mOutlierDistribution.mN++;
const double kDelta = diff - mOutlierDistribution.mMean;
mOutlierDistribution.mMean += kDelta / mOutlierDistribution.mN;
const double kDelta2 = diff - mOutlierDistribution.mMean;
mOutlierDistribution.mM2 += kDelta * kDelta2;
mOutlierDistribution.mSd = (mOutlierDistribution.mN < 2) ? 0 :
sqrt(mOutlierDistribution.mM2 / (mOutlierDistribution.mN - 1));
} else {
// new value is far from the mean:
// store peak timestamp and reset mean, sd, and short-term sequence
isPeak = true;
mPeakTimestamps.emplace_front(ts);
// if mPeaks has reached capacity, delete oldest data
// Note: this means that mOutlierDistribution values do not exactly
// match the data we have in mPeakTimestamps, but this is not an issue
// in practice for estimating future peaks.
// TODO: turn this into a circular buffer
if (mPeakTimestamps.size() >= kMaxLength.Peaks) {
mPeakTimestamps.resize(kMaxLength.Peaks);
}
mOutlierDistribution.mMean = 0;
mOutlierDistribution.mSd = 0;
mOutlierDistribution.mN = 0;
mOutlierDistribution.mM2 = 0;
}
return isPeak;
}
// Determines whether the difference between a timestamp and the previous
// one is beyond a threshold. If yes, stores the timestamp as an outlier
// and writes to mOutlierdata in the following format:
// Time elapsed since previous outlier: Timestamp of start of outlier
// e.g. timestamps (ms) 1, 4, 5, 16, 18, 28 will produce pairs (4, 5), (13, 18).
// TODO: learn what timestamp sequences correlate with glitches instead of
// manually designing a heuristic.
bool PerformanceAnalysis::detectAndStoreOutlier(const msInterval diffMs) {
bool isOutlier = false;
if (diffMs >= mBufferPeriod.mOutlier) {
isOutlier = true;
mOutlierData.emplace_front(
mOutlierDistribution.mElapsed, mBufferPeriod.mPrevTs);
// Remove oldest value if the vector is full
// TODO: turn this into a circular buffer
// TODO: make sure kShortHistSize is large enough that that data will never be lost
// before being written to file or to a FIFO
if (mOutlierData.size() >= kMaxLength.Outliers) {
mOutlierData.resize(kMaxLength.Outliers);
}
mOutlierDistribution.mElapsed = 0;
}
mOutlierDistribution.mElapsed += diffMs;
return isOutlier;
}
// rounds value to precision based on log-distance from mean
__attribute__((no_sanitize("signed-integer-overflow")))
inline double logRound(double x, double mean) {
// Larger values decrease range of high resolution and prevent overflow
// of a histogram on the console.
// The following formula adjusts kBase based on the buffer period length.
// Different threads have buffer periods ranging from 2 to 40. The
// formula below maps buffer period 2 to kBase = ~1, 4 to ~2, 20 to ~3, 40 to ~4.
// TODO: tighten this for higher means, the data still overflows
const double kBase = log(mean) / log(2.2);
const double power = floor(
log(abs(x - mean) / mean) / log(kBase)) + 2;
// do not round values close to the mean
if (power < 1) {
return x;
}
const int factor = static_cast<int>(pow(10, power));
return (static_cast<int>(x) * factor) / factor;
}
// TODO Make it return a std::string instead of modifying body
// TODO: move this to ReportPerformance, probably make it a friend function
// of PerformanceAnalysis
void PerformanceAnalysis::reportPerformance(String8 *body, int author, log_hash_t hash,
int maxHeight) {
if (mHists.empty() || body == nullptr) {
return;
}
// ms of active audio in displayed histogram
double elapsedMs = 0;
// starting timestamp of histogram
timestamp startingTs = mHists[0].first;
// histogram which stores .1 precision ms counts instead of Jiffy multiple counts
std::map<double, int> buckets;
for (const auto &shortHist: mHists) {
for (const auto &countPair : shortHist.second) {
const double ms = static_cast<double>(countPair.first) / kJiffyPerMs;
buckets[logRound(ms, mBufferPeriod.mMean)] += countPair.second;
elapsedMs += ms * countPair.second;
}
}
static const int SIZE = 128;
char title[SIZE];
snprintf(title, sizeof(title), "\n%s %3.2f %s\n%s%d, %lld, %lld\n",
"Occurrences in", (elapsedMs / kMsPerSec), "seconds of audio:",
"Thread, hash, starting timestamp: ", author,
static_cast<long long>(hash), static_cast<long long>(startingTs));
static const char * const kLabel = "ms";
body->appendFormat("%s",
audio_utils_plot_histogram(buckets, title, kLabel, maxHeight).c_str());
// Now report glitches
body->appendFormat("\ntime elapsed between glitches and glitch timestamps:\n");
for (const auto &outlier: mOutlierData) {
body->appendFormat("%lld: %lld\n", static_cast<long long>(outlier.first),
static_cast<long long>(outlier.second));
}
}
//------------------------------------------------------------------------------
// writes summary of performance into specified file descriptor
void dump(int fd, int indent, PerformanceAnalysisMap &threadPerformanceAnalysis) {
String8 body;
#ifdef WRITE_TO_FILE
const char* const kDirectory = "/data/misc/audioserver/";
#endif
for (auto & thread : threadPerformanceAnalysis) {
for (auto & hash: thread.second) {
PerformanceAnalysis& curr = hash.second;
// write performance data to console
curr.reportPerformance(&body, thread.first, hash.first);
if (!body.isEmpty()) {
dumpLine(fd, indent, body);
body.clear();
}
#ifdef WRITE_TO_FILE
// write to file. Enable by uncommenting macro at top of file.
writeToFile(curr.mHists, curr.mOutlierData, curr.mPeakTimestamps,
kDirectory, false, thread.first, hash.first);
#endif
}
}
}
// Writes a string into specified file descriptor
void dumpLine(int fd, int indent, const String8 &body) {
dprintf(fd, "%.*s%s \n", indent, "", body.string());
}
} // namespace ReportPerformance
} // namespace android