CPU statistics library

Change-Id: I113e2a926466cc410cfa5602ceb165b390a290fc

3 files changed, 241 insertions, 0 deletions

diff --git a/libs/cpustats/Android.mk b/libs/cpustats/Android.mk
new file mode 100644
index 0000000..5c1074d
--- /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 0000000..42ab62b
--- /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 0000000..4bfbdf3
--- /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;
+        }
+    }
+}