Merge "CPU statistics library"

3 files changed, 194 insertions, 0 deletions

diff --git a/include/cpustats/CentralTendencyStatistics.h b/include/cpustats/CentralTendencyStatistics.h
new file mode 100644
index 0000000..21b6981
--- /dev/null
+++ b/include/cpustats/CentralTendencyStatistics.h
@@ -0,0 +1,75 @@
+/*
+ * 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
diff --git a/include/cpustats/README.txt b/include/cpustats/README.txt
new file mode 100644
index 0000000..14439f0
--- /dev/null
+++ b/include/cpustats/README.txt
@@ -0,0 +1,6 @@
+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
diff --git a/include/cpustats/ThreadCpuUsage.h b/include/cpustats/ThreadCpuUsage.h
new file mode 100644
index 0000000..24012a4
--- /dev/null
+++ b/include/cpustats/ThreadCpuUsage.h
@@ -0,0 +1,113 @@
+/*
+ * 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