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authorSvenn-Arne Dragly <svenn-arne.dragly@qt.io>2017-09-05 15:02:20 +0200
committerSvenn-Arne Dragly <svenn-arne.dragly@qt.io>2017-10-04 12:00:33 +0000
commitba423261cd9abedda8b732c82371515003d385ce (patch)
tree78c7a4997deaf6ae6e5b20e99f72c2f03e89f6c3 /src/corelib/thread/qthreadpool.cpp
parentd7c57fa68e7bfa1fcb1bca3bcc1ea3e3668167a9 (diff)
Improve performance in QThreadPool
When many runnables are executed, this improves the performance by not resizing the queue for each runnable, which was the case in the previous version, because of many calls to QVector::takeFirst(). Also add a test that makes sure tryTake() is safe to call and does not leave the queue in a bad state that tries to use nullptr entries. Change-Id: I608134ecfa9cfc03db4878dcbd6f9c1107e13e90 Reviewed-by: Lars Knoll <lars.knoll@qt.io>
Diffstat (limited to 'src/corelib/thread/qthreadpool.cpp')
-rw-r--r--src/corelib/thread/qthreadpool.cpp87
1 files changed, 57 insertions, 30 deletions
diff --git a/src/corelib/thread/qthreadpool.cpp b/src/corelib/thread/qthreadpool.cpp
index f3ce1f258f6..ccd8194b350 100644
--- a/src/corelib/thread/qthreadpool.cpp
+++ b/src/corelib/thread/qthreadpool.cpp
@@ -73,7 +73,7 @@ public:
\internal
*/
QThreadPoolThread::QThreadPoolThread(QThreadPoolPrivate *manager)
- :manager(manager), runnable(0)
+ :manager(manager), runnable(nullptr)
{ }
/*
@@ -84,7 +84,7 @@ void QThreadPoolThread::run()
QMutexLocker locker(&manager->mutex);
for(;;) {
QRunnable *r = runnable;
- runnable = 0;
+ runnable = nullptr;
do {
if (r) {
@@ -116,8 +116,19 @@ void QThreadPoolThread::run()
if (manager->tooManyThreadsActive())
break;
- r = !manager->queue.isEmpty() ? manager->queue.takeFirst().first : 0;
- } while (r != 0);
+ if (manager->queue.isEmpty()) {
+ r = nullptr;
+ break;
+ }
+
+ QueuePage *page = manager->queue.first();
+ r = page->pop();
+
+ if (page->isFinished()) {
+ manager->queue.removeFirst();
+ delete page;
+ }
+ } while (true);
if (manager->isExiting) {
registerThreadInactive();
@@ -163,6 +174,7 @@ QThreadPoolPrivate:: QThreadPoolPrivate()
bool QThreadPoolPrivate::tryStart(QRunnable *task)
{
+ Q_ASSERT(task != nullptr);
if (allThreads.isEmpty()) {
// always create at least one thread
startThread(task);
@@ -183,7 +195,7 @@ bool QThreadPoolPrivate::tryStart(QRunnable *task)
if (!expiredThreads.isEmpty()) {
// restart an expired thread
QThreadPoolThread *thread = expiredThreads.dequeue();
- Q_ASSERT(thread->runnable == 0);
+ Q_ASSERT(thread->runnable == nullptr);
++activeThreads;
@@ -199,22 +211,25 @@ bool QThreadPoolPrivate::tryStart(QRunnable *task)
return true;
}
-inline bool operator<(int priority, const QPair<QRunnable *, int> &p)
-{ return p.second < priority; }
-inline bool operator<(const QPair<QRunnable *, int> &p, int priority)
-{ return priority < p.second; }
+inline bool comparePriority(int priority, const QueuePage *p)
+{
+ return p->priority() < priority;
+}
void QThreadPoolPrivate::enqueueTask(QRunnable *runnable, int priority)
{
+ Q_ASSERT(runnable != nullptr);
if (runnable->autoDelete())
++runnable->ref;
- // put it on the queue
- QVector<QPair<QRunnable *, int> >::const_iterator begin = queue.constBegin();
- QVector<QPair<QRunnable *, int> >::const_iterator it = queue.constEnd();
- if (it != begin && priority > (*(it - 1)).second)
- it = std::upper_bound(begin, --it, priority);
- queue.insert(it - begin, qMakePair(runnable, priority));
+ for (QueuePage *page : qAsConst(queue)) {
+ if (page->priority() == priority && !page->isFull()) {
+ page->push(runnable);
+ return;
+ }
+ }
+ auto it = std::upper_bound(queue.constBegin(), queue.constEnd(), priority, comparePriority);
+ queue.insert(std::distance(queue.constBegin(), it), new QueuePage(runnable, priority));
}
int QThreadPoolPrivate::activeThreadCount() const
@@ -228,8 +243,18 @@ int QThreadPoolPrivate::activeThreadCount() const
void QThreadPoolPrivate::tryToStartMoreThreads()
{
// try to push tasks on the queue to any available threads
- while (!queue.isEmpty() && tryStart(queue.constFirst().first))
- queue.removeFirst();
+ while (!queue.isEmpty()) {
+ QueuePage *page = queue.first();
+ if (!tryStart(page->first()))
+ break;
+
+ page->pop();
+
+ if (page->isFinished()) {
+ queue.removeFirst();
+ delete page;
+ }
+ }
}
bool QThreadPoolPrivate::tooManyThreadsActive() const
@@ -243,6 +268,7 @@ bool QThreadPoolPrivate::tooManyThreadsActive() const
*/
void QThreadPoolPrivate::startThread(QRunnable *runnable)
{
+ Q_ASSERT(runnable != nullptr);
QScopedPointer <QThreadPoolThread> thread(new QThreadPoolThread(this));
thread->setObjectName(QLatin1String("Thread (pooled)"));
Q_ASSERT(!allThreads.contains(thread.data())); // if this assert hits, we have an ABA problem (deleted threads don't get removed here)
@@ -306,12 +332,14 @@ bool QThreadPoolPrivate::waitForDone(int msecs)
void QThreadPoolPrivate::clear()
{
QMutexLocker locker(&mutex);
- for (QVector<QPair<QRunnable *, int> >::const_iterator it = queue.constBegin();
- it != queue.constEnd(); ++it) {
- QRunnable* r = it->first;
- if (r->autoDelete() && !--r->ref)
- delete r;
+ for (QueuePage *page : qAsConst(queue)) {
+ while (!page->isFinished()) {
+ QRunnable *r = page->pop();
+ if (r && r->autoDelete() && !--r->ref)
+ delete r;
+ }
}
+ qDeleteAll(queue);
queue.clear();
}
@@ -336,22 +364,21 @@ bool QThreadPool::tryTake(QRunnable *runnable)
{
Q_D(QThreadPool);
- if (runnable == 0)
+ if (runnable == nullptr)
return false;
{
QMutexLocker locker(&d->mutex);
- auto it = d->queue.begin();
- auto end = d->queue.end();
-
- while (it != end) {
- if (it->first == runnable) {
- d->queue.erase(it);
+ for (QueuePage *page : qAsConst(d->queue)) {
+ if (page->tryTake(runnable)) {
+ if (page->isFinished()) {
+ d->queue.removeOne(page);
+ delete page;
+ }
if (runnable->autoDelete())
--runnable->ref; // undo ++ref in start()
return true;
}
- ++it;
}
}
generated by cgit v1.2.3 (git 2.25.1) at 2025-12-18 10:13:54 +0000