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123 lines
4.0 KiB
C++
123 lines
4.0 KiB
C++
//------------------------------------------------------------------------------
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/*
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This file is part of Beast: https://github.com/vinniefalco/Beast
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Copyright 2013, Vinnie Falco <vinnie.falco@gmail.com>
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Permission to use, copy, modify, and/or distribute this software for any
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purpose with or without fee is hereby granted, provided that the above
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copyright notice and this permission notice appear in all copies.
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THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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ANY SPECIAL , DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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//==============================================================================
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#ifndef BEAST_WORKERS_H_INCLUDED
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#define BEAST_WORKERS_H_INCLUDED
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/** A group of threads that process tasks.
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*/
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class Workers
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{
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public:
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/** Called to perform tasks as needed. */
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struct Callback
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{
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/** Perform a task.
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The call is made on a thread owned by Workers.
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*/
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virtual void processTask () = 0;
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};
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/** Create the object.
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A number of initial threads may be optionally specified. The
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default is to create one thread per CPU.
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*/
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explicit Workers (Callback& callback, int numberOfThreads = SystemStats::getNumCpus ());
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~Workers ();
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/** Retrieve the desired number of threads.
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This just returns the number of active threads that were requested. If
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there was a recent call to setNumberOfThreads, the actual number of active
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threads may be temporarily different from what was last requested.
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@note This function is not thread-safe.
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*/
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int getNumberOfThreads () const noexcept;
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/** Set the desired number of threads.
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@note This function is not thread-safe.
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*/
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void setNumberOfThreads (int numberOfThreads);
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/** Pause all threads and wait until they are paused.
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If a thread is processing a task it will pause as soon as the task
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completes. There may still be tasks signaled even after all threads
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have paused.
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@note This function is not thread-safe.
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*/
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void pauseAllThreadsAndWait ();
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/** Increment the number of tasks.
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The callback will be called for each task.
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@note This function is thread-safe.
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*/
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void addTask ();
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//--------------------------------------------------------------------------
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private:
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struct PausedTag { };
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/* A Worker executes tasks on its provided thread.
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These are the states:
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Active: Running the task processing loop.
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Idle: Active, but blocked on waiting for a task.
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Pausd: Blocked waiting to exit or become active.
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*/
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class Worker
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: public LockFreeStack <Worker>::Node
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, public LockFreeStack <Worker, PausedTag>::Node
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, public Thread
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{
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public:
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explicit Worker (Workers& workers);
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~Worker ();
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private:
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void run ();
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private:
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Workers& m_workers;
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};
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private:
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static void deleteWorkers (LockFreeStack <Worker>& stack);
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private:
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Callback& m_callback;
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WaitableEvent m_allPaused; // signaled when all threads paused
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Semaphore m_semaphore; // each pending task is 1 resource
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int m_numberOfThreads; // how many we want active now
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Atomic <int> m_activeCount; // to know when all are paused
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Atomic <int> m_pauseCount; // how many threads need to pause now
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LockFreeStack <Worker> m_everyone; // holds all created workers
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LockFreeStack <Worker, PausedTag> m_paused; // holds just paused workers
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};
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#endif
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