Re: vhost-net patches

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Oct 27, 2009 at 07:46:59AM -0700, Shirley Ma wrote:
> Hello Michael,
> 
> On Tue, 2009-10-27 at 08:43 +0200, Michael S. Tsirkin wrote:
> > At some point my guest had a runaway nash-hotplug process
> > consuming 100% CPU. Could you please verify this
> > does not happen to you?
> 
> What I have found that the start_xmit stopped and restarted too often.
> There is no vring descriptor available for adding the new buf. The buf
> release is not able to keep up after vhost patch?

Possibly GFP_ATOMIC allocations in vring_add_indirect are failing?
Is there a chance you are tight on guest memory for some reason?
with vhost, virtio does currently consume a bit more memory than
with userspace backend.

> I saw lots of "Unexpected full queue" from dmesg. I haven't had time to
> debug it yet. You might have some idea here?
> 
>         /* This can happen with OOM and indirect buffers. */
>         if (unlikely(capacity < 0)) {
>                 netif_stop_queue(dev);
>                 dev_warn(&dev->dev, "Unexpected full queue\n");
>                 if (unlikely(!vi->svq->vq_ops->enable_cb(vi->svq))) {
>                         vi->svq->vq_ops->disable_cb(vi->svq);
>                         netif_start_queue(dev);
>                         goto again;
>                 }
>                 return NETDEV_TX_BUSY;
>         }
> 
> Thanks
> Shirley