2012-03-26 19:18:24 +00:00
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/*
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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 <fcntl.h>
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#include <pthread.h>
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namespace android {
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// Track CPU usage for the current thread.
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// 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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// For acyclic threads, or for cyclic threads where you want to measure/track
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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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{
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(void) pthread_once(&sOnceControl, &init);
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for (int i = 0; i < sKernelMax; ++i) {
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mCurrentkHz[i] = (uint32_t) ~0; // unknown
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}
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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() const { 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, and also enable tracking if needed.
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// If tracking has never been enabled, then this call enables tracking but
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// does _not_ add a sample -- it is not possible to add a sample the
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// first time because there is no previous point to subtract from.
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// Otherwise, if tracking is enabled,
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// 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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// Returns true if the sample 'ns' is valid, or false if invalid.
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// Note that 'ns' is an output parameter passed by reference.
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// The caller does not need to initialize this variable.
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// The units are CPU nanoseconds consumed by current thread.
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bool sampleAndEnable(double& ns);
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// Add a sample point, 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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// Returns true if the sample is valid, or false if invalid.
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// Note that 'ns' is an output parameter passed by reference.
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// The caller does not need to initialize this variable.
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// The units are CPU nanoseconds consumed by current thread.
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bool sample(double& ns);
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// Return the elapsed delta wall clock ns since initial enable or 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 elapsed wall clock. Has no effect on tracking or accumulator.
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void resetElapsed();
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// Return current clock frequency for specified CPU, in kHz.
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// You can get your CPU number using sched_getcpu(2). Note that, unless CPU affinity
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// has been configured appropriately, the CPU number can change.
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// Also note that, unless the CPU governor has been configured appropriately,
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// the CPU frequency can change. And even if the CPU frequency is locked down
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// to a particular value, that the frequency might still be adjusted
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// to prevent thermal overload. Therefore you should poll for your thread's
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// current CPU number and clock frequency periodically.
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uint32_t getCpukHz(int cpuNum);
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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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static const int MAX_CPU = 8;
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static int sScalingFds[MAX_CPU];// file descriptor per CPU for reading scaling_cur_freq
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uint32_t mCurrentkHz[MAX_CPU]; // current CPU frequency in kHz, not static to avoid a race
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static pthread_once_t sOnceControl;
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static int sKernelMax; // like MAX_CPU, but determined at runtime == cpu/kernel_max + 1
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2012-05-14 17:49:17 +00:00
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static void init(); // called once at first ThreadCpuUsage construction
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static pthread_mutex_t sMutex; // protects sScalingFds[] after initialization
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2012-03-26 19:18:24 +00:00
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};
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} // namespace android
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#endif // _THREAD_CPU_USAGE_H
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