Add benchmark for QThreadPool.

The current question is whether activeThreadCount() should be lock-free
(using atomic ints) or mutex-protected, so this tests start()
and activeThreadCount() directly.

Change-Id: Ica4a2ad023c2002e3c7d81558e6b9ee64af7f690
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>

tests/benchmarks/corelib/thread/qthreadpool/qthreadpool.pro

@@ -0,0 +1,5 @@
+TEMPLATE = app
+TARGET = tst_bench_qthreadpool
+
+SOURCES += tst_qthreadpool.cpp
+QT = core testlib

tests/benchmarks/corelib/thread/qthreadpool/tst_qthreadpool.cpp

@@ -0,0 +1,92 @@
+/****************************************************************************
+**
+** Copyright (C) 2013 David Faure <david.faure@kdab.com>
+** Contact: http://www.qt-project.org/legal
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and Digia.  For licensing terms and
+** conditions see http://qt.digia.com/licensing.  For further information
+** use the contact form at http://qt.digia.com/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, 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, Digia gives you certain additional
+** rights.  These rights are described in the Digia 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.
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <qtest.h>
+#include <QtCore>
+
+class tst_QThreadPool : public QObject
+{
+    Q_OBJECT
+
+public:
+    tst_QThreadPool();
+    ~tst_QThreadPool();
+
+private slots:
+    void startRunnables();
+    void activeThreadCount();
+};
+
+tst_QThreadPool::tst_QThreadPool()
+{
+}
+
+tst_QThreadPool::~tst_QThreadPool()
+{
+}
+
+class NoOpRunnable : public QRunnable
+{
+public:
+    void run() Q_DECL_OVERRIDE {
+    }
+};
+
+void tst_QThreadPool::startRunnables()
+{
+    QThreadPool threadPool;
+    threadPool.setMaxThreadCount(10);
+    QBENCHMARK {
+        threadPool.start(new NoOpRunnable());
+    }
+}
+
+void tst_QThreadPool::activeThreadCount()
+{
+    QThreadPool threadPool;
+    threadPool.start(new NoOpRunnable());
+    QBENCHMARK {
+        QVERIFY(threadPool.activeThreadCount() <= 10);
+    }
+}
+
+QTEST_MAIN(tst_QThreadPool)
+#include "tst_qthreadpool.moc"

tests/benchmarks/corelib/thread/thread.pro

@@ -1,4 +1,5 @@
 TEMPLATE = subdirs
 SUBDIRS = \
         qmutex \
-        qthreadstorage
+        qthreadstorage \
+        qthreadpool \