1 files changed, 194 insertions, 0 deletions
diff --git a/src/concurrent/qtconcurrentiteratekernel.cpp b/src/concurrent/qtconcurrentiteratekernel.cpp
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+/****************************************************************************
+**
+** Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies).
+** Contact: http://www.qt-project.org/
+**
+** This file is part of the QtCore module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** GNU Lesser General Public License Usage
+** This file may be used under the terms of the GNU Lesser General Public
+** License version 2.1 as published by the Free Software Foundation and
+** appearing in the file LICENSE.LGPL included in the packaging of this
+** file. Please review the following information to ensure the GNU Lesser
+** General Public License version 2.1 requirements will be met:
+** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Nokia gives you certain additional
+** rights. These rights are described in the Nokia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU General
+** Public License version 3.0 as published by the Free Software Foundation
+** and appearing in the file LICENSE.GPL included in the packaging of this
+** file. Please review the following information to ensure the GNU General
+** Public License version 3.0 requirements will be met:
+** http://www.gnu.org/copyleft/gpl.html.
+**
+** Other Usage
+** Alternatively, this file may be used in accordance with the terms and
+** conditions contained in a signed written agreement between you and Nokia.
+**
+**
+**
+**
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qtconcurrentiteratekernel.h"
+
+#if defined(Q_OS_MAC)
+#include <mach/mach.h>
+#include <mach/mach_time.h>
+#include <unistd.h>
+#elif defined(Q_OS_UNIX)
+#if defined(Q_OS_HURD)
+#include <sys/time.h>
+#endif
+#include <time.h>
+#include <unistd.h>
+#elif defined(Q_OS_WIN)
+#include <qt_windows.h>
+#endif
+
+#include "private/qfunctions_p.h"
+
+
+#ifndef QT_NO_CONCURRENT
+
+QT_BEGIN_NAMESPACE
+
+enum {
+    TargetRatio = 100,
+    MedianSize = 7
+};
+
+#if defined(Q_OS_MAC)
+
+static qint64 getticks()
+{
+    return mach_absolute_time();
+}
+
+#elif defined(Q_OS_UNIX)
+
+
+static qint64 getticks()
+{
+#if defined(_POSIX_TIMERS) && (_POSIX_TIMERS > 0)
+    clockid_t clockId;
+
+#ifndef _POSIX_THREAD_CPUTIME
+    clockId = CLOCK_REALTIME;
+#elif (_POSIX_THREAD_CPUTIME-0 <= 0)
+    // if we don't have CLOCK_THREAD_CPUTIME_ID, we have to just use elapsed realtime instead
+    clockId = CLOCK_REALTIME;
+
+#  if (_POSIX_THREAD_CPUTIME-0 == 0)
+    // detect availablility of CLOCK_THREAD_CPUTIME_ID
+    static long useThreadCpuTime = -2;
+    if (useThreadCpuTime == -2) {
+        // sysconf() will return either -1 or _POSIX_VERSION (don't care about thread races here)
+        useThreadCpuTime = sysconf(_SC_THREAD_CPUTIME);
+    }
+    if (useThreadCpuTime != -1)
+        clockId = CLOCK_THREAD_CPUTIME_ID;
+#  endif
+#else
+    clockId = CLOCK_THREAD_CPUTIME_ID;
+#endif
+
+    struct timespec ts;
+    if (clock_gettime(clockId, &ts) == -1)
+        return 0;
+    return (ts.tv_sec * 1000000000) + ts.tv_nsec;
+#else
+
+    // no clock_gettime(), fall back to wall time
+    struct timeval tv;
+    gettimeofday(&tv, 0);
+    return (tv.tv_sec * 1000000) + tv.tv_usec;
+#endif
+}
+
+#elif defined(Q_OS_WIN)
+
+static qint64 getticks()
+{
+    LARGE_INTEGER x;
+    if (!QueryPerformanceCounter(&x))
+        return 0;
+    return x.QuadPart;
+}
+
+#endif
+
+static double elapsed(qint64 after, qint64 before)
+{
+    return double(after - before);
+}
+
+namespace QtConcurrent {
+
+/*! \internal
+
+*/
+BlockSizeManager::BlockSizeManager(int iterationCount)
+: maxBlockSize(iterationCount / (QThreadPool::globalInstance()->maxThreadCount() * 2)),
+  beforeUser(0), afterUser(0),
+  controlPartElapsed(MedianSize), userPartElapsed(MedianSize),
+  m_blockSize(1)
+{ }
+
+// Records the time before user code.
+void BlockSizeManager::timeBeforeUser()
+{
+    if (blockSizeMaxed())
+        return;
+
+    beforeUser = getticks();
+    controlPartElapsed.addValue(elapsed(beforeUser, afterUser));
+}
+
+ // Records the time after user code and adjust the block size if we are spending
+ // to much time in the for control code compared with the user code.
+void BlockSizeManager::timeAfterUser()
+{
+    if (blockSizeMaxed())
+        return;
+
+    afterUser = getticks();
+    userPartElapsed.addValue(elapsed(afterUser, beforeUser));
+
+    if (controlPartElapsed.isMedianValid() == false)
+        return;
+
+    if (controlPartElapsed.median() * TargetRatio < userPartElapsed.median())
+        return;
+
+    m_blockSize = qMin(m_blockSize * 2,  maxBlockSize);
+
+#ifdef QTCONCURRENT_FOR_DEBUG
+    qDebug() << QThread::currentThread() << "adjusting block size" << controlPartElapsed.median() << userPartElapsed.median() << m_blockSize;
+#endif
+
+    // Reset the medians after adjusting the block size so we get
+    // new measurements with the new block size.
+    controlPartElapsed.reset();
+    userPartElapsed.reset();
+}
+
+int BlockSizeManager::blockSize()
+{
+    return m_blockSize;
+}
+
+} // namespace QtConcurrent
+
+QT_END_NAMESPACE
+
+#endif // QT_NO_CONCURRENT