/include/cpustats/ThreadCpuUsage.h
http://github.com/CyanogenMod/android_frameworks_base · C++ Header · 113 lines · 34 code · 17 blank · 62 comment · 0 complexity · b2ceacb901799a01b4d814dcb1298550 MD5 · raw file
- /*
- * 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