114 lines
4.9 KiB
C++
114 lines
4.9 KiB
C++
/*
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* Copyright (C) 2011 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef _THREAD_CPU_USAGE_H
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#define _THREAD_CPU_USAGE_H
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#include <cpustats/CentralTendencyStatistics.h>
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// Track CPU usage for the current thread, and maintain statistics on
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// the CPU usage. Units are in per-thread CPU ns, as reported by
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// clock_gettime(CLOCK_THREAD_CPUTIME_ID). Simple usage: for cyclic
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// threads where you want to measure the execution time of the whole
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// cycle, just call sampleAndEnable() at the start of each cycle.
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// Then call statistics() to get the results, and resetStatistics()
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// to start a new set of measurements.
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// For acyclic threads, or for cyclic threads where you want to measure
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// only part of each cycle, call enable(), disable(), and/or setEnabled()
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// to demarcate the region(s) of interest, and then call sample() periodically.
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// This class is not thread-safe for concurrent calls from multiple threads;
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// the methods of this class may only be called by the current thread
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// which constructed the object.
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class ThreadCpuUsage
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{
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public:
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ThreadCpuUsage() :
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mIsEnabled(false),
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mWasEverEnabled(false),
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mAccumulator(0),
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// mPreviousTs
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// mMonotonicTs
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mMonotonicKnown(false)
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// mStatistics
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{ }
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~ThreadCpuUsage() { }
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// Return whether currently tracking CPU usage by current thread
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bool isEnabled() { return mIsEnabled; }
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// Enable tracking of CPU usage by current thread;
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// any CPU used from this point forward will be tracked.
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// Returns the previous enabled status.
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bool enable() { return setEnabled(true); }
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// Disable tracking of CPU usage by current thread;
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// any CPU used from this point forward will be ignored.
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// Returns the previous enabled status.
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bool disable() { return setEnabled(false); }
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// Set the enabled status and return the previous enabled status.
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// This method is intended to be used for safe nested enable/disabling.
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bool setEnabled(bool isEnabled);
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// Add a sample point for central tendency statistics, and also
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// enable tracking if needed. If tracking has never been enabled, then
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// enables tracking but does not add a sample (it is not possible to add
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// a sample the first time because no previous). Otherwise if tracking is
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// enabled, then adds a sample for tracked CPU ns since the previous
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// sample, or since the first call to sampleAndEnable(), enable(), or
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// setEnabled(true). If there was a previous sample but tracking is
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// now disabled, then adds a sample for the tracked CPU ns accumulated
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// up until the most recent disable(), resets this accumulator, and then
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// enables tracking. Calling this method rather than enable() followed
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// by sample() avoids a race condition for the first sample.
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void sampleAndEnable();
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// Add a sample point for central tendency statistics, but do not
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// change the tracking enabled status. If tracking has either never been
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// enabled, or has never been enabled since the last sample, then log a warning
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// and don't add sample. Otherwise, adds a sample for tracked CPU ns since
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// the previous sample or since the first call to sampleAndEnable(),
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// enable(), or setEnabled(true) if no previous sample.
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void sample();
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// Return the elapsed delta wall clock ns since initial enable or statistics reset,
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// as reported by clock_gettime(CLOCK_MONOTONIC).
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long long elapsed() const;
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// Reset statistics and elapsed. Has no effect on tracking or accumulator.
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void resetStatistics();
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// Return a const reference to the central tendency statistics.
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// Note that only the const methods can be called on this object.
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const CentralTendencyStatistics& statistics() const {
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return mStatistics;
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}
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private:
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bool mIsEnabled; // whether tracking is currently enabled
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bool mWasEverEnabled; // whether tracking was ever enabled
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long long mAccumulator; // accumulated thread CPU time since last sample, in ns
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struct timespec mPreviousTs; // most recent thread CPU time, valid only if mIsEnabled is true
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struct timespec mMonotonicTs; // most recent monotonic time
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bool mMonotonicKnown; // whether mMonotonicTs has been set
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CentralTendencyStatistics mStatistics;
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};
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#endif // _THREAD_CPU_USAGE_H
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