[Qemu-devel] [PATCH] virtio-scsi: dataplane: suppress guest notification

[Ming Lei]

This patch uses vring_should_notify() to suppress
guest notification, and looks notification frequency
can be decreased from ~33K/sec to ~2K/sec in my test
environment.

Suggested-by: Stefan Hajnoczi <stefa...@redhat.com>
Signed-off-by: Ming Lei <ming....@canonical.com>
---
 hw/scsi/virtio-scsi-dataplane.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/hw/scsi/virtio-scsi-dataplane.c b/hw/scsi/virtio-scsi-dataplane.c
index df17229..be3b042 100644
--- a/hw/scsi/virtio-scsi-dataplane.c
+++ b/hw/scsi/virtio-scsi-dataplane.c
@@ -93,9 +93,14 @@ VirtIOSCSIReq *virtio_scsi_pop_req_vring(VirtIOSCSI *s,
 
 void virtio_scsi_vring_push_notify(VirtIOSCSIReq *req)
 {
+    VirtIODevice *vdev = VIRTIO_DEVICE(req->vring->parent);
+
     vring_push(&req->vring->vring, &req->elem,
                req->qsgl.size + req->resp_iov.size);
-    event_notifier_set(&req->vring->guest_notifier);
+
+    if (vring_should_notify(vdev, &req->vring->vring)) {
+        event_notifier_set(&req->vring->guest_notifier);
+    }
 }
 
 static void virtio_scsi_iothread_handle_ctrl(EventNotifier *notifier)
-- 
1.7.9.5