wtf/ParallelJobsGeneric.h

   1 /*
   2  * Copyright (C) 2011 University of Szeged
   3  * Copyright (C) 2011 Gabor Loki <loki@webkit.org>
   4  * All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  * 1. Redistributions of source code must retain the above copyright
  10  *    notice, this list of conditions and the following disclaimer.
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in the
  13  *    documentation and/or other materials provided with the distribution.
  14  *
  15  * THIS SOFTWARE IS PROVIDED BY UNIVERSITY OF SZEGED ``AS IS'' AND ANY
  16  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  17  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  18  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL UNIVERSITY OF SZEGED OR
  19  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  20  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  21  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  22  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  23  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  24  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  25  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  26  */
  27
  28 #ifndef ParallelJobsGeneric_h
  29 #define ParallelJobsGeneric_h
  30
  31 #if ENABLE(THREADING_GENERIC)
  32
  33 #include <wtf/RefCounted.h>
  34 #include <wtf/Threading.h>
  35
  36 namespace WTF {
  37
  38 static const unsigned int maxParallelThreads = 2;
  39
  40 class ParallelEnvironment {
  41     WTF_MAKE_FAST_ALLOCATED;
  42 public:
  43     typedef void (*ThreadFunction)(void*);
  44
  45     ParallelEnvironment(ThreadFunction threadFunction, size_t sizeOfParameter, unsigned int requestedJobNumber) :
  46         m_threadFunction(threadFunction),
  47         m_sizeOfParameter(sizeOfParameter)
  48     {
  49         if (!requestedJobNumber || requestedJobNumber > maxParallelThreads)
  50             requestedJobNumber = maxParallelThreads;
  51
  52         if (!s_threadPool)
  53             s_threadPool = new Vector< RefPtr<ThreadPrivate> >();
  54
  55         // The main thread should be also a worker.
  56         unsigned int maxNewThreads = requestedJobNumber - 1;
  57
  58         for (unsigned int i = 0; i < maxParallelThreads && m_threads.size() < maxNewThreads; ++i) {
  59             if (s_threadPool->size() < i + 1)
  60                 s_threadPool->append(ThreadPrivate::create());
  61
  62             if ((*s_threadPool)[i]->tryLockFor(this))
  63                 m_threads.append((*s_threadPool)[i]);
  64         }
  65
  66         m_numberOfJobs = m_threads.size() + 1;
  67     }
  68
  69     int numberOfJobs()
  70     {
  71         return m_numberOfJobs;
  72     }
  73
  74     void execute(unsigned char* parameters)
  75     {
  76         size_t i;
  77         for (i = 0; i < m_threads.size(); ++i) {
  78             m_threads[i]->execute(m_threadFunction, parameters);
  79             parameters += m_sizeOfParameter;
  80         }
  81
  82         // The work for the main thread
  83         (*m_threadFunction)(parameters);
  84
  85         // Wait until all jobs are done.
  86         for (i = 0; i < m_threads.size(); ++i)
  87             m_threads[i]->waitForFinish();
  88     }
  89
  90     class ThreadPrivate : public RefCounted<ThreadPrivate> {
  91     public:
  92         ThreadPrivate()
  93             : m_threadID(0)
  94             , m_running(false)
  95             , m_parent(0)
  96         {
  97         }
  98
  99         bool tryLockFor(ParallelEnvironment*);
 100
 101         void execute(ThreadFunction, void*);
 102
 103         void waitForFinish();
 104
 105         static PassRefPtr<ThreadPrivate> create()
 106         {
 107             return adoptRef(new ThreadPrivate());
 108         }
 109
 110         static void* workerThread(void*);
 111
 112     private:
 113         ThreadIdentifier m_threadID;
 114         bool m_running;
 115         ParallelEnvironment* m_parent;
 116
 117         mutable Mutex m_mutex;
 118         ThreadCondition m_threadCondition;
 119
 120         ThreadFunction m_threadFunction;
 121         void* m_parameters;
 122     };
 123
 124 private:
 125     ThreadFunction m_threadFunction;
 126     size_t m_sizeOfParameter;
 127     int m_numberOfJobs;
 128
 129     Vector< RefPtr<ThreadPrivate> > m_threads;
 130     static Vector< RefPtr<ThreadPrivate> >* s_threadPool;
 131 };
 132
 133 } // namespace WTF
 134
 135 #endif // ENABLE(THREADING_GENERIC)
 136
 137
 138 #endif // ParallelJobsGeneric_h