2946cd7010
to reflect the new license. We understand that people may be surprised that we're moving the header entirely to discuss the new license. We checked this carefully with the Foundation's lawyer and we believe this is the correct approach. Essentially, all code in the project is now made available by the LLVM project under our new license, so you will see that the license headers include that license only. Some of our contributors have contributed code under our old license, and accordingly, we have retained a copy of our old license notice in the top-level files in each project and repository. llvm-svn: 351636
119 lines
3.2 KiB
C++
119 lines
3.2 KiB
C++
//===--------------------- TaskPool.cpp -------------------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "lldb/Host/TaskPool.h"
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#include "lldb/Host/ThreadLauncher.h"
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#include <cstdint>
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#include <queue>
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#include <thread>
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namespace lldb_private {
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namespace {
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class TaskPoolImpl {
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public:
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static TaskPoolImpl &GetInstance();
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void AddTask(std::function<void()> &&task_fn);
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private:
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TaskPoolImpl();
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static lldb::thread_result_t WorkerPtr(void *pool);
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static void Worker(TaskPoolImpl *pool);
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std::queue<std::function<void()>> m_tasks;
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std::mutex m_tasks_mutex;
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uint32_t m_thread_count;
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};
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} // end of anonymous namespace
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TaskPoolImpl &TaskPoolImpl::GetInstance() {
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static TaskPoolImpl g_task_pool_impl;
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return g_task_pool_impl;
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}
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void TaskPool::AddTaskImpl(std::function<void()> &&task_fn) {
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TaskPoolImpl::GetInstance().AddTask(std::move(task_fn));
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}
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TaskPoolImpl::TaskPoolImpl() : m_thread_count(0) {}
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unsigned GetHardwareConcurrencyHint() {
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// std::thread::hardware_concurrency may return 0 if the value is not well
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// defined or not computable.
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static const unsigned g_hardware_concurrency =
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std::max(1u, std::thread::hardware_concurrency());
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return g_hardware_concurrency;
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}
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void TaskPoolImpl::AddTask(std::function<void()> &&task_fn) {
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const size_t min_stack_size = 8 * 1024 * 1024;
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std::unique_lock<std::mutex> lock(m_tasks_mutex);
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m_tasks.emplace(std::move(task_fn));
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if (m_thread_count < GetHardwareConcurrencyHint()) {
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m_thread_count++;
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// Note that this detach call needs to happen with the m_tasks_mutex held.
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// This prevents the thread from exiting prematurely and triggering a linux
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// libc bug (https://sourceware.org/bugzilla/show_bug.cgi?id=19951).
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lldb_private::ThreadLauncher::LaunchThread("task-pool.worker", WorkerPtr,
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this, nullptr, min_stack_size)
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.Release();
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}
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}
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lldb::thread_result_t TaskPoolImpl::WorkerPtr(void *pool) {
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Worker((TaskPoolImpl *)pool);
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return 0;
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}
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void TaskPoolImpl::Worker(TaskPoolImpl *pool) {
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while (true) {
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std::unique_lock<std::mutex> lock(pool->m_tasks_mutex);
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if (pool->m_tasks.empty()) {
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pool->m_thread_count--;
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break;
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}
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std::function<void()> f = std::move(pool->m_tasks.front());
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pool->m_tasks.pop();
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lock.unlock();
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f();
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}
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}
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void TaskMapOverInt(size_t begin, size_t end,
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const llvm::function_ref<void(size_t)> &func) {
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const size_t num_workers = std::min<size_t>(end, GetHardwareConcurrencyHint());
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std::atomic<size_t> idx{begin};
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auto wrapper = [&idx, end, &func]() {
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while (true) {
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size_t i = idx.fetch_add(1);
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if (i >= end)
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break;
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func(i);
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}
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};
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std::vector<std::future<void>> futures;
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futures.reserve(num_workers);
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for (size_t i = 0; i < num_workers; i++)
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futures.push_back(TaskPool::AddTask(wrapper));
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for (size_t i = 0; i < num_workers; i++)
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futures[i].wait();
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}
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} // namespace lldb_private
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