Abseil Common Libraries (C++) (grcp 依赖)
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190 lines
6.5 KiB
190 lines
6.5 KiB
// Copyright 2018 The Abseil Authors. |
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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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// https://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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#include "absl/container/internal/hashtablez_sampler.h" |
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#include <atomic> |
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#include <cassert> |
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#include <cmath> |
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#include <functional> |
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#include <limits> |
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#include "absl/base/attributes.h" |
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#include "absl/container/internal/have_sse.h" |
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#include "absl/debugging/stacktrace.h" |
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#include "absl/memory/memory.h" |
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#include "absl/profiling/internal/exponential_biased.h" |
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#include "absl/profiling/internal/sample_recorder.h" |
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#include "absl/synchronization/mutex.h" |
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namespace absl { |
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ABSL_NAMESPACE_BEGIN |
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namespace container_internal { |
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constexpr int HashtablezInfo::kMaxStackDepth; |
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namespace { |
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ABSL_CONST_INIT std::atomic<bool> g_hashtablez_enabled{ |
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false |
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}; |
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ABSL_CONST_INIT std::atomic<int32_t> g_hashtablez_sample_parameter{1 << 10}; |
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#if defined(ABSL_INTERNAL_HASHTABLEZ_SAMPLE) |
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ABSL_PER_THREAD_TLS_KEYWORD absl::profiling_internal::ExponentialBiased |
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g_exponential_biased_generator; |
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#endif |
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} // namespace |
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#if defined(ABSL_INTERNAL_HASHTABLEZ_SAMPLE) |
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ABSL_PER_THREAD_TLS_KEYWORD int64_t global_next_sample = 0; |
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#endif // defined(ABSL_INTERNAL_HASHTABLEZ_SAMPLE) |
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HashtablezSampler& GlobalHashtablezSampler() { |
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static auto* sampler = new HashtablezSampler(); |
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return *sampler; |
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} |
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// TODO(bradleybear): The comments at this constructors declaration say that the |
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// fields are not initialized, but this definition does initialize the fields. |
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// Something needs to be cleaned up. |
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HashtablezInfo::HashtablezInfo() { PrepareForSampling(); } |
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HashtablezInfo::~HashtablezInfo() = default; |
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void HashtablezInfo::PrepareForSampling() { |
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capacity.store(0, std::memory_order_relaxed); |
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size.store(0, std::memory_order_relaxed); |
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num_erases.store(0, std::memory_order_relaxed); |
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num_rehashes.store(0, std::memory_order_relaxed); |
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max_probe_length.store(0, std::memory_order_relaxed); |
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total_probe_length.store(0, std::memory_order_relaxed); |
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hashes_bitwise_or.store(0, std::memory_order_relaxed); |
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hashes_bitwise_and.store(~size_t{}, std::memory_order_relaxed); |
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hashes_bitwise_xor.store(0, std::memory_order_relaxed); |
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max_reserve.store(0, std::memory_order_relaxed); |
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create_time = absl::Now(); |
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// The inliner makes hardcoded skip_count difficult (especially when combined |
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// with LTO). We use the ability to exclude stacks by regex when encoding |
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// instead. |
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depth = absl::GetStackTrace(stack, HashtablezInfo::kMaxStackDepth, |
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/* skip_count= */ 0); |
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} |
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static bool ShouldForceSampling() { |
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enum ForceState { |
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kDontForce, |
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kForce, |
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kUninitialized |
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}; |
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ABSL_CONST_INIT static std::atomic<ForceState> global_state{ |
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kUninitialized}; |
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ForceState state = global_state.load(std::memory_order_relaxed); |
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if (ABSL_PREDICT_TRUE(state == kDontForce)) return false; |
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if (state == kUninitialized) { |
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state = ABSL_INTERNAL_C_SYMBOL(AbslContainerInternalSampleEverything)() |
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? kForce |
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: kDontForce; |
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global_state.store(state, std::memory_order_relaxed); |
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} |
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return state == kForce; |
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} |
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HashtablezInfo* SampleSlow(int64_t* next_sample, size_t inline_element_size) { |
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if (ABSL_PREDICT_FALSE(ShouldForceSampling())) { |
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*next_sample = 1; |
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HashtablezInfo* result = GlobalHashtablezSampler().Register(); |
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result->inline_element_size = inline_element_size; |
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return result; |
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} |
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#if !defined(ABSL_INTERNAL_HASHTABLEZ_SAMPLE) |
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*next_sample = std::numeric_limits<int64_t>::max(); |
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return nullptr; |
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#else |
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bool first = *next_sample < 0; |
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*next_sample = g_exponential_biased_generator.GetStride( |
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g_hashtablez_sample_parameter.load(std::memory_order_relaxed)); |
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// Small values of interval are equivalent to just sampling next time. |
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ABSL_ASSERT(*next_sample >= 1); |
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// g_hashtablez_enabled can be dynamically flipped, we need to set a threshold |
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// low enough that we will start sampling in a reasonable time, so we just use |
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// the default sampling rate. |
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if (!g_hashtablez_enabled.load(std::memory_order_relaxed)) return nullptr; |
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// We will only be negative on our first count, so we should just retry in |
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// that case. |
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if (first) { |
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if (ABSL_PREDICT_TRUE(--*next_sample > 0)) return nullptr; |
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return SampleSlow(next_sample, inline_element_size); |
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} |
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HashtablezInfo* result = GlobalHashtablezSampler().Register(); |
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result->inline_element_size = inline_element_size; |
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return result; |
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#endif |
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} |
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void UnsampleSlow(HashtablezInfo* info) { |
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GlobalHashtablezSampler().Unregister(info); |
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} |
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void RecordInsertSlow(HashtablezInfo* info, size_t hash, |
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size_t distance_from_desired) { |
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// SwissTables probe in groups of 16, so scale this to count items probes and |
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// not offset from desired. |
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size_t probe_length = distance_from_desired; |
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#if ABSL_INTERNAL_RAW_HASH_SET_HAVE_SSE2 |
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probe_length /= 16; |
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#else |
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probe_length /= 8; |
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#endif |
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info->hashes_bitwise_and.fetch_and(hash, std::memory_order_relaxed); |
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info->hashes_bitwise_or.fetch_or(hash, std::memory_order_relaxed); |
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info->hashes_bitwise_xor.fetch_xor(hash, std::memory_order_relaxed); |
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info->max_probe_length.store( |
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std::max(info->max_probe_length.load(std::memory_order_relaxed), |
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probe_length), |
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std::memory_order_relaxed); |
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info->total_probe_length.fetch_add(probe_length, std::memory_order_relaxed); |
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info->size.fetch_add(1, std::memory_order_relaxed); |
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} |
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void SetHashtablezEnabled(bool enabled) { |
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g_hashtablez_enabled.store(enabled, std::memory_order_release); |
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} |
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void SetHashtablezSampleParameter(int32_t rate) { |
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if (rate > 0) { |
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g_hashtablez_sample_parameter.store(rate, std::memory_order_release); |
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} else { |
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ABSL_RAW_LOG(ERROR, "Invalid hashtablez sample rate: %lld", |
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static_cast<long long>(rate)); // NOLINT(runtime/int) |
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} |
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} |
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void SetHashtablezMaxSamples(int32_t max) { |
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if (max > 0) { |
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GlobalHashtablezSampler().SetMaxSamples(max); |
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} else { |
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ABSL_RAW_LOG(ERROR, "Invalid hashtablez max samples: %lld", |
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static_cast<long long>(max)); // NOLINT(runtime/int) |
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} |
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} |
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} // namespace container_internal |
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ABSL_NAMESPACE_END |
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} // namespace absl
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