[PATCH] vhost: get 2% performance improved by reducing spin_lock race in vhost_work_queue

[Qinchuanyu <qinchuanyu@xxxxxxxxxx>]

Right now the wake_up_process func is included in spin_lock/unlock, but it could be done outside the spin_lock.
I have test it with kernel 3.0.27 and guest suse11-sp2, it provide 2%-3% net performance improved.

Signed-off-by: Chuanyu Qin <qinchuanyu@xxxxxxxxxx>
--- a/drivers/vhost/vhost.c     2013-05-20 10:36:30.000000000 +0800
+++ b/drivers/vhost/vhost.c     2013-05-20 10:36:54.000000000 +0800
@@ -144,9 +144,10 @@
        if (list_empty(&work->node)) {
                list_add_tail(&work->node, &dev->work_list);
                work->queue_seq++;
+               spin_unlock_irqrestore(&dev->work_lock, flags);
                wake_up_process(dev->worker);
-       }
-       spin_unlock_irqrestore(&dev->work_lock, flags);
+       } else
+               spin_unlock_irqrestore(&dev->work_lock, flags);
 }
 
 void vhost_poll_queue(struct vhost_poll *poll)
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html