periodic_sampler.cc (1592B)
1 // Copyright 2019 The Abseil Authors. 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // https://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 #include "absl/profiling/internal/periodic_sampler.h" 16 17 #include <atomic> 18 19 #include "absl/profiling/internal/exponential_biased.h" 20 21 namespace absl { 22 ABSL_NAMESPACE_BEGIN 23 namespace profiling_internal { 24 25 int64_t PeriodicSamplerBase::GetExponentialBiased(int period) noexcept { 26 return rng_.GetStride(period); 27 } 28 29 bool PeriodicSamplerBase::SubtleConfirmSample() noexcept { 30 int current_period = period(); 31 32 // Deal with period case 0 (always off) and 1 (always on) 33 if (ABSL_PREDICT_FALSE(current_period < 2)) { 34 stride_ = 0; 35 return current_period == 1; 36 } 37 38 // Check if this is the first call to Sample() 39 if (ABSL_PREDICT_FALSE(stride_ == 1)) { 40 stride_ = static_cast<uint64_t>(-GetExponentialBiased(current_period)); 41 if (static_cast<int64_t>(stride_) < -1) { 42 ++stride_; 43 return false; 44 } 45 } 46 47 stride_ = static_cast<uint64_t>(-GetExponentialBiased(current_period)); 48 return true; 49 } 50 51 } // namespace profiling_internal 52 ABSL_NAMESPACE_END 53 } // namespace absl