From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56933) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1c788s-0003V8-1I for qemu-devel@nongnu.org; Wed, 16 Nov 2016 16:53:18 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1c788r-0006Rj-CP for qemu-devel@nongnu.org; Wed, 16 Nov 2016 16:53:18 -0500 Received: from mx1.redhat.com ([209.132.183.28]:43040) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1c788r-0006RO-6e for qemu-devel@nongnu.org; Wed, 16 Nov 2016 16:53:17 -0500 From: Stefan Hajnoczi Date: Wed, 16 Nov 2016 21:53:08 +0000 Message-Id: <1479333189-20082-3-git-send-email-stefanha@redhat.com> In-Reply-To: <1479333189-20082-1-git-send-email-stefanha@redhat.com> References: <1479333189-20082-1-git-send-email-stefanha@redhat.com> Subject: [Qemu-devel] [PATCH 2/3] virtio-blk: suppress virtqueue kick during processing List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: zhunxun@gmail.com, Fam Zheng , Christian Borntraeger , Paolo Bonzini , "Michael S. Tsirkin" , Kevin Wolf , Stefan Hajnoczi The guest does not need to kick the virtqueue while we are processing it. This reduces the number of vmexits during periods of heavy I/O. Signed-off-by: Stefan Hajnoczi --- hw/block/virtio-blk.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c index 0c5fd27..50bb0cb 100644 --- a/hw/block/virtio-blk.c +++ b/hw/block/virtio-blk.c @@ -588,13 +588,19 @@ void virtio_blk_handle_vq(VirtIOBlock *s, VirtQueue *vq) blk_io_plug(s->blk); - while ((req = virtio_blk_get_request(s, vq))) { - if (virtio_blk_handle_request(req, &mrb)) { - virtqueue_detach_element(req->vq, &req->elem, 0); - virtio_blk_free_request(req); - break; + do { + virtio_queue_set_notification(vq, 0); + + while ((req = virtio_blk_get_request(s, vq))) { + if (virtio_blk_handle_request(req, &mrb)) { + virtqueue_detach_element(req->vq, &req->elem, 0); + virtio_blk_free_request(req); + break; + } } - } + + virtio_queue_set_notification(vq, 1); + } while (!virtio_queue_empty(vq)); if (mrb.num_reqs) { virtio_blk_submit_multireq(s->blk, &mrb); -- 2.7.4