0818b0921e
Makes it easy to schedule a bunch of work to happen in parallel. Change-Id: Id9c0e52fc8b6d78d2b9ed4c2ee47abce0a01775c
120 lines
3.8 KiB
C++
120 lines
3.8 KiB
C++
/*]
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* Copyright (C) 2012 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef _LIBS_UTILS_WORK_QUEUE_H
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#define _LIBS_UTILS_WORK_QUEUE_H
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#include <utils/Errors.h>
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#include <utils/Vector.h>
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#include <utils/threads.h>
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namespace android {
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/*
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* A threaded work queue.
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*
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* This class is designed to make it easy to run a bunch of isolated work
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* units in parallel, using up to the specified number of threads.
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* To use it, write a loop to post work units to the work queue, then synchronize
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* on the queue at the end.
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*/
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class WorkQueue {
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public:
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class WorkUnit {
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public:
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WorkUnit() { }
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virtual ~WorkUnit() { }
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/*
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* Runs the work unit.
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* If the result is 'true' then the work queue continues scheduling work as usual.
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* If the result is 'false' then the work queue is canceled.
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*/
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virtual bool run() = 0;
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};
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/* Creates a work queue with the specified maximum number of work threads. */
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WorkQueue(size_t maxThreads, bool canCallJava = true);
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/* Destroys the work queue.
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* Cancels pending work and waits for all remaining threads to complete.
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*/
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~WorkQueue();
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/* Posts a work unit to run later.
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* If the work queue has been canceled or is already finished, returns INVALID_OPERATION
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* and does not take ownership of the work unit (caller must destroy it itself).
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* Otherwise, returns OK and takes ownership of the work unit (the work queue will
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* destroy it automatically).
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*
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* For flow control, this method blocks when the size of the pending work queue is more
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* 'backlog' times the number of threads. This condition reduces the rate of entry into
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* the pending work queue and prevents it from growing much more rapidly than the
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* work threads can actually handle.
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*
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* If 'backlog' is 0, then no throttle is applied.
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*/
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status_t schedule(WorkUnit* workUnit, size_t backlog = 2);
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/* Cancels all pending work.
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* If the work queue is already finished, returns INVALID_OPERATION.
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* If the work queue is already canceled, returns OK and does nothing else.
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* Otherwise, returns OK, discards all pending work units and prevents additional
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* work units from being scheduled.
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*
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* Call finish() after cancel() to wait for all remaining work to complete.
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*/
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status_t cancel();
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/* Waits for all work to complete.
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* If the work queue is already finished, returns INVALID_OPERATION.
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* Otherwise, waits for all work to complete and returns OK.
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*/
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status_t finish();
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private:
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class WorkThread : public Thread {
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public:
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WorkThread(WorkQueue* workQueue, bool canCallJava);
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virtual ~WorkThread();
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private:
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virtual bool threadLoop();
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WorkQueue* const mWorkQueue;
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};
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status_t cancelLocked();
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bool threadLoop(); // called from each work thread
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const size_t mMaxThreads;
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const bool mCanCallJava;
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Mutex mLock;
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Condition mWorkChangedCondition;
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Condition mWorkDequeuedCondition;
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bool mCanceled;
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bool mFinished;
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size_t mIdleThreads;
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Vector<sp<WorkThread> > mWorkThreads;
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Vector<WorkUnit*> mWorkUnits;
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};
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}; // namespace android
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#endif // _LIBS_UTILS_WORK_QUEUE_H
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