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llvm-project/libcxx/test/benchmarks/atomic_wait_multi_waiter_1_notifier.bench.cpp
Louis Dionne 815b1641a6
[libc++] Disable atomic_wait benchmarks outside of dry-run mode (#158631) 
The atomic_wait benchmarks are great, but they tend to overload the
system they're running on. For that reason, we can't run them on our CI
infrastructure on a regular basis.

Instead of removing them, make them unsupported outside of dry-running,
which allows keeping the benchmarks around and ensuring they don't rot,
but doesn't run them along with the other benchmarks. If we need to
investigate atomic_wait performance, it's trivial to mark the benchmark
as supported and run it for local investigations.

This is an alternative to https://github.com/llvm/llvm-project/pull/158289.
2025-09-19 10:54:18 -04:00

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//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
// UNSUPPORTED: c++03, c++11, c++14, c++17
// This benchmark is very expensive and we don't want to run it on a regular basis,
// only to ensure the code doesn't rot.
// REQUIRES: enable-benchmarks=dry-run
#include "atomic_wait_helper.h"
#include <atomic>
#include <cstdint>
#include <numeric>
#include <stop_token>
#include <thread>
#include <chrono>
#include <array>
#include "benchmark/benchmark.h"
#include "make_test_thread.h"
using namespace std::chrono_literals;
template <class NotifyPolicy, class NumWaitingThreads, class NumPrioTasks>
void BM_1_atomic_multi_waiter_1_notifier(benchmark::State& state) {
[[maybe_unused]] std::array<HighPrioTask, NumPrioTasks::value> tasks{};
std::atomic<std::uint64_t> a;
auto notify_func = [&](std::stop_token st) { NotifyPolicy::notify(a, st); };
std::uint64_t total_loop_test_param = state.range(0);
constexpr auto num_waiting_threads = NumWaitingThreads::value;
std::vector<std::jthread> wait_threads;
wait_threads.reserve(num_waiting_threads);
auto notify_thread = support::make_test_jthread(notify_func);
std::atomic<std::uint64_t> start_flag = 0;
std::atomic<std::uint64_t> done_count = 0;
auto wait_func = [&a, &start_flag, &done_count, total_loop_test_param](std::stop_token st) {
auto old_start = 0;
while (!st.stop_requested()) {
start_flag.wait(old_start);
old_start = start_flag.load();
for (std::uint64_t i = 0; i < total_loop_test_param; ++i) {
auto old = a.load(std::memory_order_relaxed);
a.wait(old);
}
done_count.fetch_add(1);
}
};
for (size_t i = 0; i < num_waiting_threads; ++i) {
wait_threads.emplace_back(support::make_test_jthread(wait_func));
}
for (auto _ : state) {
done_count = 0;
start_flag.fetch_add(1);
start_flag.notify_all();
while (done_count < num_waiting_threads) {
std::this_thread::yield();
}
}
for (auto& t : wait_threads) {
t.request_stop();
}
start_flag.fetch_add(1);
start_flag.notify_all();
for (auto& t : wait_threads) {
t.join();
}
}
BENCHMARK(BM_1_atomic_multi_waiter_1_notifier<KeepNotifying, NumWaitingThreads<3>, NumHighPrioTasks<0>>)
->RangeMultiplier(2)
->Range(1 << 14, 1 << 16);
BENCHMARK(BM_1_atomic_multi_waiter_1_notifier<KeepNotifying, NumWaitingThreads<7>, NumHighPrioTasks<0>>)
->RangeMultiplier(2)
->Range(1 << 12, 1 << 14);
BENCHMARK(BM_1_atomic_multi_waiter_1_notifier<KeepNotifying, NumWaitingThreads<15>, NumHighPrioTasks<0>>)
->RangeMultiplier(2)
->Range(1 << 10, 1 << 12);
BENCHMARK(BM_1_atomic_multi_waiter_1_notifier<NotifyEveryNus<50>, NumWaitingThreads<3>, NumHighPrioTasks<0>>)
->RangeMultiplier(2)
->Range(1 << 10, 1 << 12);
BENCHMARK(BM_1_atomic_multi_waiter_1_notifier<NotifyEveryNus<50>, NumWaitingThreads<7>, NumHighPrioTasks<0>>)
->RangeMultiplier(2)
->Range(1 << 8, 1 << 10);
BENCHMARK(BM_1_atomic_multi_waiter_1_notifier<NotifyEveryNus<50>, NumWaitingThreads<15>, NumHighPrioTasks<0>>)
->RangeMultiplier(2)
->Range(1 << 6, 1 << 8);
BENCHMARK(BM_1_atomic_multi_waiter_1_notifier<NotifyEveryNus<100>, NumWaitingThreads<3>, NumHighPrioTasks<0>>)
->RangeMultiplier(2)
->Range(1 << 8, 1 << 10);
BENCHMARK(BM_1_atomic_multi_waiter_1_notifier<NotifyEveryNus<100>, NumWaitingThreads<7>, NumHighPrioTasks<0>>)
->RangeMultiplier(2)
->Range(1 << 6, 1 << 8);
BENCHMARK(BM_1_atomic_multi_waiter_1_notifier<NotifyEveryNus<100>, NumWaitingThreads<15>, NumHighPrioTasks<0>>)
->RangeMultiplier(2)
->Range(1 << 4, 1 << 6);
BENCHMARK(BM_1_atomic_multi_waiter_1_notifier<KeepNotifying, NumWaitingThreads<3>, NumHighPrioTasks<4>>)
->RangeMultiplier(2)
->Range(1 << 8, 1 << 10);
BENCHMARK(BM_1_atomic_multi_waiter_1_notifier<KeepNotifying, NumWaitingThreads<7>, NumHighPrioTasks<4>>)
->RangeMultiplier(2)
->Range(1 << 6, 1 << 8);
BENCHMARK(BM_1_atomic_multi_waiter_1_notifier<KeepNotifying, NumWaitingThreads<15>, NumHighPrioTasks<4>>)
->RangeMultiplier(2)
->Range(1 << 4, 1 << 6);
BENCHMARK(BM_1_atomic_multi_waiter_1_notifier<NotifyEveryNus<50>, NumWaitingThreads<3>, NumHighPrioTasks<4>>)
->RangeMultiplier(2)
->Range(1 << 8, 1 << 10);
BENCHMARK(BM_1_atomic_multi_waiter_1_notifier<NotifyEveryNus<50>, NumWaitingThreads<7>, NumHighPrioTasks<4>>)
->RangeMultiplier(2)
->Range(1 << 6, 1 << 8);
BENCHMARK(BM_1_atomic_multi_waiter_1_notifier<NotifyEveryNus<50>, NumWaitingThreads<15>, NumHighPrioTasks<4>>)
->RangeMultiplier(2)
->Range(1 << 4, 1 << 6);
BENCHMARK(BM_1_atomic_multi_waiter_1_notifier<NotifyEveryNus<100>, NumWaitingThreads<3>, NumHighPrioTasks<4>>)
->RangeMultiplier(2)
->Range(1 << 8, 1 << 10);
BENCHMARK(BM_1_atomic_multi_waiter_1_notifier<NotifyEveryNus<100>, NumWaitingThreads<7>, NumHighPrioTasks<4>>)
->RangeMultiplier(2)
->Range(1 << 6, 1 << 8);
BENCHMARK(BM_1_atomic_multi_waiter_1_notifier<NotifyEveryNus<100>, NumWaitingThreads<15>, NumHighPrioTasks<4>>)
->RangeMultiplier(2)
->Range(1 << 4, 1 << 6);
BENCHMARK(BM_1_atomic_multi_waiter_1_notifier<KeepNotifying, NumWaitingThreads<3>, NumHighPrioTasks<7>>)
->RangeMultiplier(2)
->Range(1 << 4, 1 << 6);
BENCHMARK(BM_1_atomic_multi_waiter_1_notifier<KeepNotifying, NumWaitingThreads<7>, NumHighPrioTasks<7>>)
->RangeMultiplier(2)
->Range(1 << 3, 1 << 5);
BENCHMARK(BM_1_atomic_multi_waiter_1_notifier<KeepNotifying, NumWaitingThreads<15>, NumHighPrioTasks<7>>)
->RangeMultiplier(2)
->Range(1 << 2, 1 << 4);
BENCHMARK(BM_1_atomic_multi_waiter_1_notifier<NotifyEveryNus<50>, NumWaitingThreads<3>, NumHighPrioTasks<7>>)
->RangeMultiplier(2)
->Range(1 << 3, 1 << 5);
BENCHMARK(BM_1_atomic_multi_waiter_1_notifier<NotifyEveryNus<50>, NumWaitingThreads<7>, NumHighPrioTasks<7>>)
->RangeMultiplier(2)
->Range(1 << 2, 1 << 4);
BENCHMARK(BM_1_atomic_multi_waiter_1_notifier<NotifyEveryNus<50>, NumWaitingThreads<15>, NumHighPrioTasks<7>>)
->RangeMultiplier(2)
->Range(1 << 1, 1 << 3);
BENCHMARK(BM_1_atomic_multi_waiter_1_notifier<NotifyEveryNus<100>, NumWaitingThreads<3>, NumHighPrioTasks<7>>)
->RangeMultiplier(2)
->Range(1 << 3, 1 << 5);
BENCHMARK(BM_1_atomic_multi_waiter_1_notifier<NotifyEveryNus<100>, NumWaitingThreads<7>, NumHighPrioTasks<7>>)
->RangeMultiplier(2)
->Range(1 << 2, 1 << 4);
BENCHMARK(BM_1_atomic_multi_waiter_1_notifier<NotifyEveryNus<100>, NumWaitingThreads<15>, NumHighPrioTasks<7>>)
->RangeMultiplier(2)
->Range(1 << 1, 1 << 3);
BENCHMARK_MAIN();
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