From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bart Van Assche Subject: [PATCH 1/2] vhost: Reduce vhost_work_flush() wakeup latency Date: Wed, 14 Aug 2013 09:02:32 +0200 Message-ID: <520B2B88.6020307@acm.org> References: <520B2B47.9040002@acm.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Asias He , kvm-devel To: "Michael S. Tsirkin" Return-path: Received: from juliette.telenet-ops.be ([195.130.137.74]:43818 "EHLO juliette.telenet-ops.be" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752942Ab3HNHCd (ORCPT ); Wed, 14 Aug 2013 03:02:33 -0400 In-Reply-To: <520B2B47.9040002@acm.org> Sender: kvm-owner@vger.kernel.org List-ID: If the TIF_NEED_RESCHED task flag is set, wake up any vhost_work_flush() waiters before rescheduling instead of after rescheduling. Signed-off-by: Bart Van Assche Cc: Michael S. Tsirkin Cc: Asias He --- drivers/vhost/vhost.c | 42 +++++++++++++++++++----------------------- 1 file changed, 19 insertions(+), 23 deletions(-) diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index e58cf00..e7ffc10 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -201,47 +201,43 @@ static void vhost_vq_reset(struct vhost_dev *dev, static int vhost_worker(void *data) { struct vhost_dev *dev = data; - struct vhost_work *work = NULL; - unsigned uninitialized_var(seq); + struct vhost_work *work; + unsigned seq; mm_segment_t oldfs = get_fs(); set_fs(USER_DS); use_mm(dev->mm); - for (;;) { + spin_lock_irq(&dev->work_lock); + while (!kthread_should_stop()) { /* mb paired w/ kthread_stop */ set_current_state(TASK_INTERRUPTIBLE); - - spin_lock_irq(&dev->work_lock); - if (work) { - work->done_seq = seq; - if (work->flushing) - wake_up_all(&work->done); - } - - if (kthread_should_stop()) { - spin_unlock_irq(&dev->work_lock); - __set_current_state(TASK_RUNNING); - break; - } if (!list_empty(&dev->work_list)) { work = list_first_entry(&dev->work_list, struct vhost_work, node); list_del_init(&work->node); seq = work->queue_seq; - } else - work = NULL; - spin_unlock_irq(&dev->work_lock); + spin_unlock_irq(&dev->work_lock); - if (work) { __set_current_state(TASK_RUNNING); work->fn(work); - if (need_resched()) - schedule(); - } else + + spin_lock_irq(&dev->work_lock); + work->done_seq = seq; + if (work->flushing) + wake_up_all(&work->done); + } + if (list_empty(&dev->work_list) || need_resched()) { + spin_unlock_irq(&dev->work_lock); + schedule(); + spin_lock_irq(&dev->work_lock); + } } + spin_unlock_irq(&dev->work_lock); + + __set_current_state(TASK_RUNNING); unuse_mm(dev->mm); set_fs(oldfs); return 0; -- 1.7.10.4