1 /* 2 * Copyright (C) 2020 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef ART_RUNTIME_JAVAHEAPPROF_JAVAHEAPSAMPLER_H_ 18 #define ART_RUNTIME_JAVAHEAPPROF_JAVAHEAPSAMPLER_H_ 19 20 #include <random> 21 #include "base/locks.h" 22 #include "base/mutex.h" 23 #include "mirror/object.h" 24 25 namespace art { 26 27 class HeapSampler { 28 public: HeapSampler()29 HeapSampler() : rng_(/*seed=*/std::minstd_rand::default_seed), 30 geo_dist_(1.0 / /*expected value=4KB*/ 4096), 31 geo_dist_rng_lock_("Heap Sampler RNG Geometric Dist lock", 32 art::LockLevel::kGenericBottomLock) {} 33 34 // Set the bytes until sample. SetBytesUntilSample(size_t bytes)35 void SetBytesUntilSample(size_t bytes) { 36 *GetBytesUntilSample() = bytes; 37 } 38 // Get the bytes until sample. GetBytesUntilSample()39 size_t* GetBytesUntilSample() { 40 // Initialization should happen only once the first time the function is called. 41 // However there will always be a slot allocated for it at thread creation. 42 thread_local size_t bytes_until_sample = 0; 43 return &bytes_until_sample; 44 } SetHeapID(uint32_t heap_id)45 void SetHeapID(uint32_t heap_id) { 46 perfetto_heap_id_ = heap_id; 47 } EnableHeapSampler()48 void EnableHeapSampler() { 49 enabled_.store(true, std::memory_order_release); 50 } DisableHeapSampler()51 void DisableHeapSampler() { 52 enabled_.store(false, std::memory_order_release); 53 } 54 // Report a sample to Perfetto. 55 void ReportSample(art::mirror::Object* obj, size_t allocation_size); 56 // Check whether we should take a sample or not at this allocation, and return the 57 // number of bytes from current pos to the next sample to use in the expand Tlab 58 // calculation. 59 // Update state of both take_sample and temp_bytes_until_sample. 60 // tlab_used = pos - start 61 // Note: we do not update bytes until sample here. It will be saved after the allocation 62 // happens. This function can be called before the actual allocation happens. 63 size_t GetSampleOffset(size_t alloc_size, 64 size_t tlab_used, 65 bool* take_sample, 66 size_t* temp_bytes_until_sample) REQUIRES(!geo_dist_rng_lock_); 67 // Adjust the sample offset value with the adjustment usually (pos - start) 68 // of new Tlab after Reset. 69 void AdjustSampleOffset(size_t adjustment); 70 // Is heap sampler enabled? 71 bool IsEnabled(); 72 // Set the sampling interval. 73 void SetSamplingInterval(int sampling_interval) REQUIRES(!geo_dist_rng_lock_); 74 // Return the sampling interval. 75 int GetSamplingInterval(); 76 77 private: 78 size_t NextGeoDistRandSample() REQUIRES(!geo_dist_rng_lock_); 79 // Choose, save, and return the number of bytes until the next sample, 80 // possibly decreasing sample intervals by sample_adj_bytes. 81 size_t PickAndAdjustNextSample(size_t sample_adj_bytes = 0) REQUIRES(!geo_dist_rng_lock_); 82 83 std::atomic<bool> enabled_; 84 // Default sampling interval is 4kb. 85 // Writes guarded by geo_dist_rng_lock_. 86 std::atomic<int> p_sampling_interval_{4 * 1024}; 87 uint32_t perfetto_heap_id_ = 0; 88 // std random number generator. 89 std::minstd_rand rng_ GUARDED_BY(geo_dist_rng_lock_); // Holds the state 90 // std geometric distribution 91 std::geometric_distribution</*result_type=*/size_t> geo_dist_ GUARDED_BY(geo_dist_rng_lock_); 92 // Multiple threads can access the geometric distribution and the random number 93 // generator concurrently and thus geo_dist_rng_lock_ is used for thread safety. 94 art::Mutex geo_dist_rng_lock_; 95 }; 96 97 } // namespace art 98 99 #endif // ART_RUNTIME_JAVAHEAPPROF_JAVAHEAPSAMPLER_H_ 100