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. > > This patch modifies virtqueue_kick() to optionally release a lock while > notifying the host. Virtio block is modified to pass in its lock. This > allows other vcpus to queue I/O requests during the time spent servicing > the virtqueue notify in the host. > > The virtqueue_kick() function is modified to know about locking because > it changes the state of the virtqueue and should execute with the lock > held (it would not be correct for virtio block to release the lock > before calling virtqueue_kick()). > > Signed-off-by: Stefan Hajnoczi <stefanha@xxxxxxxxxxxxxxxxxx> While the optimization makes sense, the API's pretty hairy IMHO. Why don't we split the kick functionality instead? E.g. /* Report whether host notification is necessary. */ bool virtqueue_kick_prepare(struct virtqueue *vq) /* Can be done in parallel with add_buf/get_buf */ void virtqueue_kick_notify(struct virtqueue *vq) And users can r = virtqueue_kick_prepare(vq); spin_unlock_irqrestore(...); if (r) virtqueue_kick_notify(struct virtqueue *vq) -- MST _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/virtualization
