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diff --git a/src/rocksdb/util/threadpool_imp.h b/src/rocksdb/util/threadpool_imp.h
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+++ b/src/rocksdb/util/threadpool_imp.h
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+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+#pragma once
+
+#include <functional>
+#include <memory>
+
+#include "rocksdb/env.h"
+#include "rocksdb/threadpool.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+class ThreadPoolImpl : public ThreadPool {
+ public:
+  ThreadPoolImpl();
+  ~ThreadPoolImpl();
+
+  ThreadPoolImpl(ThreadPoolImpl&&) = delete;
+  ThreadPoolImpl& operator=(ThreadPoolImpl&&) = delete;
+
+  // Implement ThreadPool interfaces
+
+  // Wait for all threads to finish.
+  // Discards all the jobs that did not
+  // start executing and waits for those running
+  // to complete
+  void JoinAllThreads() override;
+
+  // Set the number of background threads that will be executing the
+  // scheduled jobs.
+  void SetBackgroundThreads(int num) override;
+  int GetBackgroundThreads() override;
+
+  // Get the number of jobs scheduled in the ThreadPool queue.
+  unsigned int GetQueueLen() const override;
+
+  // Waits for all jobs to complete those
+  // that already started running and those that did not
+  // start yet
+  void WaitForJobsAndJoinAllThreads() override;
+
+  // Make threads to run at a lower kernel IO priority
+  // Currently only has effect on Linux
+  void LowerIOPriority();
+
+  // Make threads to run at a lower kernel CPU priority
+  // Currently only has effect on Linux
+  void LowerCPUPriority(CpuPriority pri);
+
+  // Ensure there is at aleast num threads in the pool
+  // but do not kill threads if there are more
+  void IncBackgroundThreadsIfNeeded(int num);
+
+  // Submit a fire and forget job
+  // These jobs can not be unscheduled
+
+  // This allows to submit the same job multiple times
+  void SubmitJob(const std::function<void()>&) override;
+  // This moves the function in for efficiency
+  void SubmitJob(std::function<void()>&&) override;
+
+  // Schedule a job with an unschedule tag and unschedule function
+  // Can be used to filter and unschedule jobs by a tag
+  // that are still in the queue and did not start running
+  void Schedule(void (*function)(void* arg1), void* arg, void* tag,
+                void (*unschedFunction)(void* arg));
+
+  // Filter jobs that are still in a queue and match
+  // the given tag. Remove them from a queue if any
+  // and for each such job execute an unschedule function
+  // if such was given at scheduling time.
+  int UnSchedule(void* tag);
+
+  void SetHostEnv(Env* env);
+
+  Env* GetHostEnv() const;
+
+  // Return the thread priority.
+  // This would allow its member-thread to know its priority.
+  Env::Priority GetThreadPriority() const;
+
+  // Set the thread priority.
+  void SetThreadPriority(Env::Priority priority);
+
+  // Reserve a specific number of threads, prevent them from running other
+  // functions The number of reserved threads could be fewer than the desired
+  // one
+  int ReserveThreads(int threads_to_be_reserved) override;
+
+  // Release a specific number of threads
+  int ReleaseThreads(int threads_to_be_released) override;
+
+  static void PthreadCall(const char* label, int result);
+
+  struct Impl;
+
+ private:
+  // Current public virtual interface does not provide usable
+  // functionality and thus can not be used internally to
+  // facade different implementations.
+  //
+  // We propose a pimpl idiom in order to easily replace the thread pool impl
+  // w/o touching the header file but providing a different .cc potentially
+  // CMake option driven.
+  //
+  // Another option is to introduce a Env::MakeThreadPool() virtual interface
+  // and override the environment. This would require refactoring ThreadPool
+  // usage.
+  //
+  // We can also combine these two approaches
+  std::unique_ptr<Impl> impl_;
+};
+
+}  // namespace ROCKSDB_NAMESPACE