Fix performance regression on Mac OS X when creating/destroying QMutex

This reverts commit cf17b743d2fe84ab259b7232ab07b58a1872e18e, which
changed QMutex to use a Mach semaphore_t on Mac OS X. We now use
pthread_mutex_t on Mac OS X as well. Contention performance is mostly
unchanged, but the new constructionQMutex() benchmark added in this
commit shows that creating/destroying a semaphore_t is about 20 times
slower than pthread_mutex_t.

Reviewed-by: Olivier Goffart
Reviewed-by: João Abecasis

1 files changed, 19 insertions, 0 deletions

diff --git a/tests/benchmarks/corelib/thread/qmutex/tst_qmutex.cpp b/tests/benchmarks/corelib/thread/qmutex/tst_qmutex.cpp
index 05a15750c1..eca38b6b5f 100644
--- a/tests/benchmarks/corelib/thread/qmutex/tst_qmutex.cpp
+++ b/tests/benchmarks/corelib/thread/qmutex/tst_qmutex.cpp
@@ -128,7 +128,9 @@ private slots:
     void noThread_data();
     void noThread();
 
+    void constructionNative();
     void uncontendedNative();
+    void constructionQMutex();
     void uncontendedQMutex();
     void uncontendedQMutexLocker();
 
@@ -205,6 +207,15 @@ void tst_QMutex::noThread()
     QCOMPARE(int(count), N);
 }
 
+void tst_QMutex::constructionNative()
+{
+    QBENCHMARK {
+        NativeMutexType mutex;
+        NativeMutexInitialize(&mutex);
+        NativeMutexDestroy(&mutex);
+    }
+}
+
 void tst_QMutex::uncontendedNative()
 {
     NativeMutexType mutex;
@@ -216,6 +227,14 @@ void tst_QMutex::uncontendedNative()
     NativeMutexDestroy(&mutex);
 }
 
+void tst_QMutex::constructionQMutex()
+{
+    QBENCHMARK {
+        QMutex mutex;
+        Q_UNUSED(mutex);
+    }
+}
+
 void tst_QMutex::uncontendedQMutex()
 {
     QMutex mutex;