| Andrew Walbran | 3d2c197 | 2020-04-07 12:24:26 +0100 | [diff] [blame^] | 1 | //===--------------------- TaskPool.h ---------------------------*- C++ -*-===// |
| 2 | // |
| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| 4 | // See https://llvm.org/LICENSE.txt for license information. |
| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| 6 | // |
| 7 | //===----------------------------------------------------------------------===// |
| 8 | |
| 9 | #ifndef utility_TaskPool_h_ |
| 10 | #define utility_TaskPool_h_ |
| 11 | |
| 12 | #include "llvm/ADT/STLExtras.h" |
| 13 | #include <functional> |
| 14 | #include <future> |
| 15 | #include <list> |
| 16 | #include <memory> |
| 17 | #include <mutex> |
| 18 | #include <type_traits> |
| 19 | |
| 20 | namespace lldb_private { |
| 21 | |
| 22 | // Global TaskPool class for running tasks in parallel on a set of worker |
| 23 | // thread created the first time the task pool is used. The TaskPool provide no |
| 24 | // guarantee about the order the task will be run and about what tasks will run |
| 25 | // in parallel. None of the task added to the task pool should block on |
| 26 | // something (mutex, future, condition variable) what will be set only by the |
| 27 | // completion of an other task on the task pool as they may run on the same |
| 28 | // thread sequentally. |
| 29 | class TaskPool { |
| 30 | public: |
| 31 | // Add a new task to the task pool and return a std::future belonging to the |
| 32 | // newly created task. The caller of this function has to wait on the future |
| 33 | // for this task to complete. |
| 34 | template <typename F, typename... Args> |
| 35 | static std::future<typename std::result_of<F(Args...)>::type> |
| 36 | AddTask(F &&f, Args &&... args); |
| 37 | |
| 38 | // Run all of the specified tasks on the task pool and wait until all of them |
| 39 | // are finished before returning. This method is intended to be used for |
| 40 | // small number tasks where listing them as function arguments is acceptable. |
| 41 | // For running large number of tasks you should use AddTask for each task and |
| 42 | // then call wait() on each returned future. |
| 43 | template <typename... T> static void RunTasks(T &&... tasks); |
| 44 | |
| 45 | private: |
| 46 | TaskPool() = delete; |
| 47 | |
| 48 | template <typename... T> struct RunTaskImpl; |
| 49 | |
| 50 | static void AddTaskImpl(std::function<void()> &&task_fn); |
| 51 | }; |
| 52 | |
| 53 | template <typename F, typename... Args> |
| 54 | std::future<typename std::result_of<F(Args...)>::type> |
| 55 | TaskPool::AddTask(F &&f, Args &&... args) { |
| 56 | auto task_sp = std::make_shared< |
| 57 | std::packaged_task<typename std::result_of<F(Args...)>::type()>>( |
| 58 | std::bind(std::forward<F>(f), std::forward<Args>(args)...)); |
| 59 | |
| 60 | AddTaskImpl([task_sp]() { (*task_sp)(); }); |
| 61 | |
| 62 | return task_sp->get_future(); |
| 63 | } |
| 64 | |
| 65 | template <typename... T> void TaskPool::RunTasks(T &&... tasks) { |
| 66 | RunTaskImpl<T...>::Run(std::forward<T>(tasks)...); |
| 67 | } |
| 68 | |
| 69 | template <typename Head, typename... Tail> |
| 70 | struct TaskPool::RunTaskImpl<Head, Tail...> { |
| 71 | static void Run(Head &&h, Tail &&... t) { |
| 72 | auto f = AddTask(std::forward<Head>(h)); |
| 73 | RunTaskImpl<Tail...>::Run(std::forward<Tail>(t)...); |
| 74 | f.wait(); |
| 75 | } |
| 76 | }; |
| 77 | |
| 78 | template <> struct TaskPool::RunTaskImpl<> { |
| 79 | static void Run() {} |
| 80 | }; |
| 81 | |
| 82 | // Run 'func' on every value from begin .. end-1. Each worker will grab |
| 83 | // 'batch_size' numbers at a time to work on, so for very fast functions, batch |
| 84 | // should be large enough to avoid too much cache line contention. |
| 85 | void TaskMapOverInt(size_t begin, size_t end, |
| 86 | const llvm::function_ref<void(size_t)> &func); |
| 87 | |
| 88 | unsigned GetHardwareConcurrencyHint(); |
| 89 | |
| 90 | } // namespace lldb_private |
| 91 | |
| 92 | #endif // #ifndef utility_TaskPool_h_ |