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Date: Mon, 11 Jan 2010 15:13:53 +0200
From: Avi Kivity <avi@redhat.com>
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Subject: Re: [Qemu-devel] Re: [RFC][PATCH] performance improvement for windows
	guests, running on top of virtio block device
References: <1263195647.2005.44.camel@localhost> <4B4AE1BD.4000400@redhat.com>
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To: Christoph Hellwig <hch@lst.de>
Cc: Dor Laor <dlaor@redhat.com>, qemu-devel <qemu-devel@nongnu.org>, Vadim Rozenfeld <vrozenfe@redhat.com>

On 01/11/2010 03:11 PM, Christoph Hellwig wrote:
> FYI below is the manually applied patch without all the wrapping:
>   static void virtio_blk_req_complete(VirtIOBlockReq *req, int status)
>   {
>       VirtIOBlock *s = req->dev;
> @@ -95,6 +98,12 @@ static void virtio_blk_req_complete(Virt
>       virtqueue_push(s->vq,&req->elem, req->qiov.size + sizeof(*req->in));
>       virtio_notify(&s->vdev, s->vq);
>
> +    if (--s->pending == 0) {
> +        virtio_queue_set_notification(s->vq, 1);
> +        virtio_blk_handle_output(&s->vdev, s->vq);
> +    }
> +
>    

As Dor points out, the call to virtio_blk_handle_output() wants to be 
before the test for pending, so we scan the ring as early as possible

-- 
error compiling committee.c: too many arguments to function