Commit 23425cc2 authored by Stefan Hajnoczi's avatar Stefan Hajnoczi
Browse files

virtio-scsi: suppress virtqueue kick during processing 



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: default avatarStefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Message-id: 20161201192652.9509-9-stefanha@redhat.com
Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
parent 9ef9d402

hw/scsi/virtio-scsi.c

+21 −15
Original line number Diff line number Diff line
@@ -592,10 +592,13 @@ static void virtio_scsi_handle_cmd_req_submit(VirtIOSCSI *s, VirtIOSCSIReq *req) 
void virtio_scsi_handle_cmd_vq(VirtIOSCSI *s, VirtQueue *vq)

{

    VirtIOSCSIReq *req, *next;

    int ret;

    int ret = 0;



    QTAILQ_HEAD(, VirtIOSCSIReq) reqs = QTAILQ_HEAD_INITIALIZER(reqs);



    do {

        virtio_queue_set_notification(vq, 0);



        while ((req = virtio_scsi_pop_req(s, vq))) {

            ret = virtio_scsi_handle_cmd_req_prepare(s, req);

            if (!ret) {
@@ -613,6 +616,9 @@ void virtio_scsi_handle_cmd_vq(VirtIOSCSI *s, VirtQueue *vq) 
            }

        }



        virtio_queue_set_notification(vq, 1);

    } while (ret != -EINVAL && !virtio_queue_empty(vq));



    QTAILQ_FOREACH_SAFE(req, &reqs, next, next) {

        virtio_scsi_handle_cmd_req_submit(s, req);

    }