On Wed, Jun 23, 2010 at 10:24:02PM +0100, Stefan Hajnoczi wrote: > The virtio block device holds a lock during I/O request processing. > Kicking the virtqueue while the lock is held results in long lock hold > times and increases contention for the lock. As you point out the problem with dropping and getting this lock in the request function is that we double the number of atomics here. How about we teach the block core to call a separate function with spinlock not held? This way we don't need to do extra lock/unlock operations, and kick can be done with lock not held and interrupts enabled. diff --git a/block/blk-core.c b/block/blk-core.c index 4ce953f..a8672ec 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -433,6 +433,8 @@ void blk_run_queue(struct request_queue *q) spin_lock_irqsave(q->queue_lock, flags); __blk_run_queue(q); spin_unlock_irqrestore(q->queue_lock, flags); + if (q->request_done) + q->request_done(q); } EXPORT_SYMBOL(blk_run_queue); -- MST -- 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
