100 lines
3.9 KiB
C++
100 lines
3.9 KiB
C++
/*
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* Copyright (C) 2020 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 ART_RUNTIME_JAVAHEAPPROF_JAVAHEAPSAMPLER_H_
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#define ART_RUNTIME_JAVAHEAPPROF_JAVAHEAPSAMPLER_H_
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#include <random>
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#include "base/locks.h"
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#include "base/mutex.h"
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#include "mirror/object.h"
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namespace art {
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class HeapSampler {
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public:
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HeapSampler() : rng_(/*seed=*/std::minstd_rand::default_seed),
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geo_dist_(1.0 / /*expected value=4KB*/ 4096),
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geo_dist_rng_lock_("Heap Sampler RNG Geometric Dist lock",
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art::LockLevel::kGenericBottomLock) {}
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// Set the bytes until sample.
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void SetBytesUntilSample(size_t bytes) {
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*GetBytesUntilSample() = bytes;
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}
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// Get the bytes until sample.
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size_t* GetBytesUntilSample() {
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// Initialization should happen only once the first time the function is called.
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// However there will always be a slot allocated for it at thread creation.
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thread_local size_t bytes_until_sample = 0;
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return &bytes_until_sample;
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}
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void SetHeapID(uint32_t heap_id) {
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perfetto_heap_id_ = heap_id;
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}
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void EnableHeapSampler() {
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enabled_.store(true, std::memory_order_release);
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}
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void DisableHeapSampler() {
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enabled_.store(false, std::memory_order_release);
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}
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// Report a sample to Perfetto.
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void ReportSample(art::mirror::Object* obj, size_t allocation_size);
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// Check whether we should take a sample or not at this allocation, and return the
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// number of bytes from current pos to the next sample to use in the expand Tlab
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// calculation.
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// Update state of both take_sample and temp_bytes_until_sample.
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// tlab_used = pos - start
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// Note: we do not update bytes until sample here. It will be saved after the allocation
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// happens. This function can be called before the actual allocation happens.
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size_t GetSampleOffset(size_t alloc_size,
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size_t tlab_used,
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bool* take_sample,
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size_t* temp_bytes_until_sample) REQUIRES(!geo_dist_rng_lock_);
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// Adjust the sample offset value with the adjustment usually (pos - start)
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// of new Tlab after Reset.
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void AdjustSampleOffset(size_t adjustment);
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// Is heap sampler enabled?
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bool IsEnabled();
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// Set the sampling interval.
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void SetSamplingInterval(int sampling_interval) REQUIRES(!geo_dist_rng_lock_);
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// Return the sampling interval.
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int GetSamplingInterval();
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private:
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size_t NextGeoDistRandSample() REQUIRES(!geo_dist_rng_lock_);
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// Choose, save, and return the number of bytes until the next sample,
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// possibly decreasing sample intervals by sample_adj_bytes.
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size_t PickAndAdjustNextSample(size_t sample_adj_bytes = 0) REQUIRES(!geo_dist_rng_lock_);
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std::atomic<bool> enabled_;
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// Default sampling interval is 4kb.
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// Writes guarded by geo_dist_rng_lock_.
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std::atomic<int> p_sampling_interval_{4 * 1024};
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uint32_t perfetto_heap_id_ = 0;
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// std random number generator.
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std::minstd_rand rng_ GUARDED_BY(geo_dist_rng_lock_); // Holds the state
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// std geometric distribution
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std::geometric_distribution</*result_type=*/size_t> geo_dist_ GUARDED_BY(geo_dist_rng_lock_);
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// Multiple threads can access the geometric distribution and the random number
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// generator concurrently and thus geo_dist_rng_lock_ is used for thread safety.
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art::Mutex geo_dist_rng_lock_;
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};
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} // namespace art
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#endif // ART_RUNTIME_JAVAHEAPPROF_JAVAHEAPSAMPLER_H_
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