| 1 | /* -*- C++ -*- |
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| 2 | This file declares the ResourceRestrictionPolicy class. |
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| 3 | |
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| 4 | SPDX-FileCopyrightText: 2004-2013 Mirko Boehm <mirko@kde.org> |
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| 5 | |
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| 6 | SPDX-License-Identifier: LGPL-2.0-or-later |
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| 7 | |
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| 8 | $Id: Job.h 32 2005-08-17 08:38:01Z mirko $ |
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| 9 | */ |
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| 10 | |
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| 11 | #ifndef RESOURCE_RESTRICTION_POLICY_H |
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| 12 | #define RESOURCE_RESTRICTION_POLICY_H |
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| 13 | |
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| 14 | #include <QtGlobal> |
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| 15 | |
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| 16 | #include "jobpointer.h" |
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| 17 | #include "queuepolicy.h" |
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| 18 | |
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| 19 | namespace ThreadWeaver |
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| 20 | { |
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| 21 | class JobInterface; |
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| 22 | |
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| 23 | /** @brief ResourceRestrictionPolicy is used to limit the number of concurrent accesses to the same resource. |
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| 24 | * |
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| 25 | * If a set of Jobs accesses a resource that can be overloaded, this may degrade application performance. For |
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| 26 | * example, loading too many files from the hard disc at the same time may lead to longer load times. |
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| 27 | * ResourceRestrictionPolicy can be used to cap the number of accesses. Resource restriction policies are |
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| 28 | * shared between the affected jobs. All jobs that share a resource restriction policy have to acquire |
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| 29 | * permission from the policy before they can run. In this way, resource restrictions can be compared to |
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| 30 | * semaphores, only that they require no locking at the thread level. |
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| 31 | * The example uses a resource restriction to limit the number of images files that are loaded from |
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| 32 | * the disk at the same time. |
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| 33 | */ |
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| 34 | |
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| 35 | class THREADWEAVER_EXPORT ResourceRestrictionPolicy : public QueuePolicy |
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| 36 | { |
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| 37 | public: |
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| 38 | explicit ResourceRestrictionPolicy(int cap = 0); |
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| 39 | ~ResourceRestrictionPolicy() override; |
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| 40 | |
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| 41 | /** @brief Cap the number of simultaneously executing jobs. |
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| 42 | * Capping the amount of jobs will make sure that at max the number of jobs executing at any time is |
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| 43 | * limited to the capped amount. Note that immediately after setting the amount of running jobs may be |
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| 44 | * higher than the set amount. This setting only limits the starting of new jobs. |
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| 45 | * @param newCap the new cap to limit the amount of parallel jobs. |
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| 46 | */ |
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| 47 | void setCap(int newCap); |
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| 48 | int cap() const; |
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| 49 | bool canRun(JobPointer) override; |
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| 50 | void free(JobPointer) override; |
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| 51 | void release(JobPointer) override; |
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| 52 | void destructed(JobInterface *job) override; |
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| 53 | |
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| 54 | private: |
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| 55 | class Private; |
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| 56 | Private *const d; |
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| 57 | }; |
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| 58 | |
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| 59 | } |
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| 60 | |
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| 61 | #endif // RESOURCE_RESTRICTION_POLICY_H |
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| 62 | |
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