1/*
2 * Copyright 2018-present Facebook, Inc.
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#pragma once
18
19#include <folly/stats/detail/DigestBuilder.h>
20
21#include <algorithm>
22
23#include <folly/concurrency/CacheLocality.h>
24
25namespace folly {
26namespace detail {
27
28static FOLLY_TLS uint32_t tls_lastCpuBufferSlot = 0;
29
30template <typename DigestT>
31DigestBuilder<DigestT>::DigestBuilder(size_t bufferSize, size_t digestSize)
32 : bufferSize_(bufferSize), digestSize_(digestSize) {
33 auto& cl = CacheLocality::system();
34 cpuLocalBuffers_.resize(cl.numCachesByLevel[0]);
35}
36
37template <typename DigestT>
38DigestT DigestBuilder<DigestT>::build() {
39 std::vector<std::vector<double>> valuesVec;
40 std::vector<std::unique_ptr<DigestT>> digestPtrs;
41 valuesVec.reserve(cpuLocalBuffers_.size());
42 digestPtrs.reserve(cpuLocalBuffers_.size());
43
44 for (auto& cpuLocalBuffer : cpuLocalBuffers_) {
45 SpinLockGuard g(cpuLocalBuffer.mutex);
46 valuesVec.push_back(std::move(cpuLocalBuffer.buffer));
47 if (cpuLocalBuffer.digest) {
48 digestPtrs.push_back(std::move(cpuLocalBuffer.digest));
49 }
50 }
51
52 std::vector<DigestT> digests;
53 for (auto& digestPtr : digestPtrs) {
54 digests.push_back(std::move(*digestPtr));
55 }
56
57 size_t count = 0;
58 for (const auto& vec : valuesVec) {
59 count += vec.size();
60 }
61 if (count) {
62 std::vector<double> values;
63 values.reserve(count);
64 for (const auto& vec : valuesVec) {
65 values.insert(values.end(), vec.begin(), vec.end());
66 }
67 DigestT digest(digestSize_);
68 digests.push_back(digest.merge(values));
69 }
70 return DigestT::merge(digests);
71}
72
73template <typename DigestT>
74void DigestBuilder<DigestT>::append(double value) {
75 auto& which = tls_lastCpuBufferSlot;
76 auto cpuLocalBuf = &cpuLocalBuffers_[which];
77 std::unique_lock<SpinLock> g(cpuLocalBuf->mutex, std::try_to_lock_t());
78 if (!g.owns_lock()) {
79 which = AccessSpreader<>::current(cpuLocalBuffers_.size());
80 cpuLocalBuf = &cpuLocalBuffers_[which];
81 g = std::unique_lock<SpinLock>(cpuLocalBuf->mutex);
82 }
83 cpuLocalBuf->buffer.push_back(value);
84 if (cpuLocalBuf->buffer.size() == bufferSize_) {
85 if (!cpuLocalBuf->digest) {
86 cpuLocalBuf->digest = std::make_unique<DigestT>(digestSize_);
87 }
88 *cpuLocalBuf->digest = cpuLocalBuf->digest->merge(cpuLocalBuf->buffer);
89 cpuLocalBuf->buffer.clear();
90 }
91}
92
93} // namespace detail
94} // namespace folly
95