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Date: Wed, 12 Nov 2014 11:19:36 +0100
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] virtio-scsi: dataplane: suppress guest
	notification
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To: Ming Lei <ming.lei@canonical.com>, qemu-devel@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>, Kevin Wolf <kwolf@redhat.com>
Cc: Fam Zheng <famz@redhat.com>, Anthony Liguori <aliguori@amazon.com>, "Michael S. Tsirkin" <mst@redhat.com>



On 12/11/2014 04:24, Ming Lei wrote:
> 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 <stefanha@redhat.com>
> Signed-off-by: Ming Lei <ming.lei@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)
> 

Thanks, applied.

Paolo