ceph/src/rocksdb/include/rocksdb/threadpool.h

   1 //  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
   2 //  This source code is licensed under both the GPLv2 (found in the
   3 //  COPYING file in the root directory) and Apache 2.0 License
   4 //  (found in the LICENSE.Apache file in the root directory).
   5 //
   6 // Copyright (c) 2011 The LevelDB Authors. All rights reserved.
   7 // Use of this source code is governed by a BSD-style license that can be
   8 // found in the LICENSE file. See the AUTHORS file for names of contributors.
   9 #pragma once
  10
  11 #include <functional>
  12
  13 namespace rocksdb {
  14
  15 /*
  16  * ThreadPool is a component that will spawn N background threads that will
  17  * be used to execute scheduled work, The number of background threads could
  18  * be modified by calling SetBackgroundThreads().
  19  * */
  20 class ThreadPool {
  21  public:
  22   virtual ~ThreadPool() {}
  23
  24   // Wait for all threads to finish.
  25   // Discard those threads that did not start
  26   // executing
  27   virtual void JoinAllThreads() = 0;
  28
  29   // Set the number of background threads that will be executing the
  30   // scheduled jobs.
  31   virtual void SetBackgroundThreads(int num) = 0;
  32   virtual int GetBackgroundThreads() = 0;
  33
  34   // Get the number of jobs scheduled in the ThreadPool queue.
  35   virtual unsigned int GetQueueLen() const = 0;
  36
  37   // Waits for all jobs to complete those
  38   // that already started running and those that did not
  39   // start yet. This ensures that everything that was thrown
  40   // on the TP runs even though
  41   // we may not have specified enough threads for the amount
  42   // of jobs
  43   virtual void WaitForJobsAndJoinAllThreads() = 0;
  44
  45   // Submit a fire and forget jobs
  46   // This allows to submit the same job multiple times
  47   virtual void SubmitJob(const std::function<void()>&) = 0;
  48   // This moves the function in for efficiency
  49   virtual void SubmitJob(std::function<void()>&&) = 0;
  50
  51 };
  52
  53 // NewThreadPool() is a function that could be used to create a ThreadPool
  54 // with `num_threads` background threads.
  55 extern ThreadPool* NewThreadPool(int num_threads);
  56
  57 }  // namespace rocksdb