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virtio-scsi: suppress virtqueue kick during processing

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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 <stefanha@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 20161201192652.9509-9-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2016-12-01 19:26:47 +00:00
parent 9ef9d40261
commit 23425cc2b7
1 changed files with 21 additions and 15 deletions
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36
hw/scsi/virtio-scsi.c
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@ -592,26 +592,32 @@ 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);
while ((req = virtio_scsi_pop_req(s, vq))) {
ret = virtio_scsi_handle_cmd_req_prepare(s, req);
if (!ret) {
QTAILQ_INSERT_TAIL(&reqs, req, next);
} else if (ret == -EINVAL) {
/* The device is broken and shouldn't process any request */
while (!QTAILQ_EMPTY(&reqs)) {
req = QTAILQ_FIRST(&reqs);
QTAILQ_REMOVE(&reqs, req, next);
blk_io_unplug(req->sreq->dev->conf.blk);
scsi_req_unref(req->sreq);
virtqueue_detach_element(req->vq, &req->elem, 0);
virtio_scsi_free_req(req);
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) {
QTAILQ_INSERT_TAIL(&reqs, req, next);
} else if (ret == -EINVAL) {
/* The device is broken and shouldn't process any request */
while (!QTAILQ_EMPTY(&reqs)) {
req = QTAILQ_FIRST(&reqs);
QTAILQ_REMOVE(&reqs, req, next);
blk_io_unplug(req->sreq->dev->conf.blk);
scsi_req_unref(req->sreq);
virtqueue_detach_element(req->vq, &req->elem, 0);
virtio_scsi_free_req(req);
}
}
}
}
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);