CPU statistics library

Change-Id: I113e2a926466cc410cfa5602ceb165b390a290fc

6 files changed, 435 insertions, 0 deletions

diff --git a/include/cpustats/CentralTendencyStatistics.h b/include/cpustats/CentralTendencyStatistics.h
new file mode 100644
index 000000000000..21b69811f615
--- /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 000000000000..14439f088722
--- /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 000000000000..24012a47f255
--- /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
diff --git a/libs/cpustats/Android.mk b/libs/cpustats/Android.mk
new file mode 100644
index 000000000000..5c1074defc25
--- /dev/null
+++ b/libs/cpustats/Android.mk
@@ -0,0 +1,21 @@
+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)
diff --git a/libs/cpustats/CentralTendencyStatistics.cpp b/libs/cpustats/CentralTendencyStatistics.cpp
new file mode 100644
index 000000000000..42ab62b4efd7
--- /dev/null
+++ b/libs/cpustats/CentralTendencyStatistics.cpp
@@ -0,0 +1,81 @@
+/*
+ * 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;
+}
diff --git a/libs/cpustats/ThreadCpuUsage.cpp b/libs/cpustats/ThreadCpuUsage.cpp
new file mode 100644
index 000000000000..4bfbdf306428
--- /dev/null
+++ b/libs/cpustats/ThreadCpuUsage.cpp
@@ -0,0 +1,139 @@
+/*
+ * 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 <errno.h>
+#include <time.h>
+
+#include <utils/Log.h>
+
+#include <cpustats/ThreadCpuUsage.h>
+
+bool ThreadCpuUsage::setEnabled(bool isEnabled)
+{
+    bool wasEnabled = mIsEnabled;
+    // only do something if there is a change
+    if (isEnabled != wasEnabled) {
+        int rc;
+        // enabling
+        if (isEnabled) {
+            rc = clock_gettime(CLOCK_THREAD_CPUTIME_ID, &mPreviousTs);
+            if (rc) {
+                LOGE("clock_gettime(CLOCK_THREAD_CPUTIME_ID) errno=%d", errno);
+                isEnabled = false;
+            } else {
+                mWasEverEnabled = true;
+                // record wall clock time at first enable
+                if (!mMonotonicKnown) {
+                    rc = clock_gettime(CLOCK_MONOTONIC, &mMonotonicTs);
+                    if (rc) {
+                        LOGE("clock_gettime(CLOCK_MONOTONIC) errno=%d", errno);
+                    } else {
+                        mMonotonicKnown = true;
+                    }
+                }
+            }
+        // disabling
+        } else {
+            struct timespec ts;
+            rc = clock_gettime(CLOCK_THREAD_CPUTIME_ID, &ts);
+            if (rc) {
+                LOGE("clock_gettime(CLOCK_THREAD_CPUTIME_ID) errno=%d", errno);
+            } else {
+                long long delta = (ts.tv_sec - mPreviousTs.tv_sec) * 1000000000LL +
+                        (ts.tv_nsec - mPreviousTs.tv_nsec);
+                mAccumulator += delta;
+#if 0
+                mPreviousTs = ts;
+#endif
+            }
+        }
+        mIsEnabled = isEnabled;
+    }
+    return wasEnabled;
+}
+
+void ThreadCpuUsage::sampleAndEnable()
+{
+    bool wasEverEnabled = mWasEverEnabled;
+    if (enable()) {
+        // already enabled, so add a new sample relative to previous
+        sample();
+    } else if (wasEverEnabled) {
+        // was disabled, but add sample for accumulated time while enabled
+        mStatistics.sample((double) mAccumulator);
+        mAccumulator = 0;
+    }
+}
+
+void ThreadCpuUsage::sample()
+{
+    if (mWasEverEnabled) {
+        if (mIsEnabled) {
+            struct timespec ts;
+            int rc;
+            rc = clock_gettime(CLOCK_THREAD_CPUTIME_ID, &ts);
+            if (rc) {
+                LOGE("clock_gettime(CLOCK_THREAD_CPUTIME_ID) errno=%d", errno);
+            } else {
+                long long delta = (ts.tv_sec - mPreviousTs.tv_sec) * 1000000000LL +
+                        (ts.tv_nsec - mPreviousTs.tv_nsec);
+                mAccumulator += delta;
+                mPreviousTs = ts;
+            }
+        } else {
+            mWasEverEnabled = false;
+        }
+        mStatistics.sample((double) mAccumulator);
+        mAccumulator = 0;
+    } else {
+        LOGW("Can't add sample because measurements have never been enabled");
+    }
+}
+
+long long ThreadCpuUsage::elapsed() const
+{
+    long long elapsed;
+    if (mMonotonicKnown) {
+        struct timespec ts;
+        int rc;
+        rc = clock_gettime(CLOCK_MONOTONIC, &ts);
+        if (rc) {
+            LOGE("clock_gettime(CLOCK_MONOTONIC) errno=%d", errno);
+            elapsed = 0;
+        } else {
+            // mMonotonicTs is updated only at first enable and resetStatistics
+            elapsed = (ts.tv_sec - mMonotonicTs.tv_sec) * 1000000000LL +
+                    (ts.tv_nsec - mMonotonicTs.tv_nsec);
+        }
+    } else {
+        LOGW("Can't compute elapsed time because measurements have never been enabled");
+        elapsed = 0;
+    }
+    return elapsed;
+}
+
+void ThreadCpuUsage::resetStatistics()
+{
+    mStatistics.reset();
+    if (mMonotonicKnown) {
+        int rc;
+        rc = clock_gettime(CLOCK_MONOTONIC, &mMonotonicTs);
+        if (rc) {
+            LOGE("clock_gettime(CLOCK_MONOTONIC) errno=%d", errno);
+            mMonotonicKnown = false;
+        }
+    }
+}