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102 lines
3.9 KiB
C++
102 lines
3.9 KiB
C++
// Jolt Physics Library (https://github.com/jrouwe/JoltPhysics)
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// SPDX-FileCopyrightText: 2021 Jorrit Rouwe
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// SPDX-License-Identifier: MIT
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#pragma once
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#include <Jolt/Core/JobSystemWithBarrier.h>
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#include <Jolt/Core/FixedSizeFreeList.h>
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#include <Jolt/Core/Semaphore.h>
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JPH_SUPPRESS_WARNINGS_STD_BEGIN
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#include <thread>
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JPH_SUPPRESS_WARNINGS_STD_END
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JPH_NAMESPACE_BEGIN
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// Things we're using from STL
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using std::thread;
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/// Implementation of a JobSystem using a thread pool
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///
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/// Note that this is considered an example implementation. It is expected that when you integrate
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/// the physics engine into your own project that you'll provide your own implementation of the
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/// JobSystem built on top of whatever job system your project uses.
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class JPH_EXPORT JobSystemThreadPool final : public JobSystemWithBarrier
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{
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public:
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JPH_OVERRIDE_NEW_DELETE
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/// Creates a thread pool.
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/// @see JobSystemThreadPool::Init
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JobSystemThreadPool(uint inMaxJobs, uint inMaxBarriers, int inNumThreads = -1);
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JobSystemThreadPool() = default;
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virtual ~JobSystemThreadPool() override;
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/// Functions to call when a thread is initialized or exits, must be set before calling Init()
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using InitExitFunction = function<void(int)>;
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void SetThreadInitFunction(const InitExitFunction &inInitFunction) { mThreadInitFunction = inInitFunction; }
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void SetThreadExitFunction(const InitExitFunction &inExitFunction) { mThreadExitFunction = inExitFunction; }
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/// Initialize the thread pool
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/// @param inMaxJobs Max number of jobs that can be allocated at any time
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/// @param inMaxBarriers Max number of barriers that can be allocated at any time
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/// @param inNumThreads Number of threads to start (the number of concurrent jobs is 1 more because the main thread will also run jobs while waiting for a barrier to complete). Use -1 to auto detect the amount of CPU's.
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void Init(uint inMaxJobs, uint inMaxBarriers, int inNumThreads = -1);
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// See JobSystem
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virtual int GetMaxConcurrency() const override { return int(mThreads.size()) + 1; }
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virtual JobHandle CreateJob(const char *inName, ColorArg inColor, const JobFunction &inJobFunction, uint32 inNumDependencies = 0) override;
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/// Change the max concurrency after initialization
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void SetNumThreads(int inNumThreads) { StopThreads(); StartThreads(inNumThreads); }
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protected:
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// See JobSystem
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virtual void QueueJob(Job *inJob) override;
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virtual void QueueJobs(Job **inJobs, uint inNumJobs) override;
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virtual void FreeJob(Job *inJob) override;
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private:
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/// Start/stop the worker threads
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void StartThreads(int inNumThreads);
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void StopThreads();
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/// Entry point for a thread
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void ThreadMain(int inThreadIndex);
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/// Get the head of the thread that has processed the least amount of jobs
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inline uint GetHead() const;
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/// Internal helper function to queue a job
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inline void QueueJobInternal(Job *inJob);
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/// Functions to call when initializing or exiting a thread
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InitExitFunction mThreadInitFunction = [](int) { };
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InitExitFunction mThreadExitFunction = [](int) { };
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/// Array of jobs (fixed size)
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using AvailableJobs = FixedSizeFreeList<Job>;
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AvailableJobs mJobs;
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/// Threads running jobs
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Array<thread> mThreads;
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// The job queue
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static constexpr uint32 cQueueLength = 1024;
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static_assert(IsPowerOf2(cQueueLength)); // We do bit operations and require queue length to be a power of 2
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atomic<Job *> mQueue[cQueueLength];
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// Head and tail of the queue, do this value modulo cQueueLength - 1 to get the element in the mQueue array
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atomic<uint> * mHeads = nullptr; ///< Per executing thread the head of the current queue
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alignas(JPH_CACHE_LINE_SIZE) atomic<uint> mTail = 0; ///< Tail (write end) of the queue
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// Semaphore used to signal worker threads that there is new work
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Semaphore mSemaphore;
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/// Boolean to indicate that we want to stop the job system
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atomic<bool> mQuit = false;
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};
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JPH_NAMESPACE_END
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