672d2c1255
This patch removes the comments following the header includes. They were added after running IWYU over the LLDB codebase. However they add little value, are often outdates and burdensome to maintain. Differential revision: https://reviews.llvm.org/D54385 llvm-svn: 346625
120 lines
3.2 KiB
C++
120 lines
3.2 KiB
C++
//===--------------------- TaskPool.cpp -------------------------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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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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