Re: [PATCH 2/4] [RFC] virtio: Introduce new API to get free space

"Michael S. Tsirkin" [off-list ref] wrote on 05/05/2011 01:30:23 AM:

quoted

quoted

@@ -185,11 +193,6 @@ int virtqueue_add_buf_gfp(struct virtque
    if (vq->num_free < out + in) {
       pr_debug("Can't add buf len %i - avail = %i\n",
           out + in, vq->num_free);
-      /* FIXME: for historical reasons, we force a notify here if
-       * there are outgoing parts to the buffer.  Presumably the
-       * host should service the ring ASAP. */
-      if (out)
-         vq->notify(&vq->vq);
       END_USE(vq);
       return -ENOSPC;
    }

This will break qemu versions 0.13 and back.
I'm adding some new virtio ring flags, we'll be
able to reuse one of these to mean 'no need for
work around', I think.

Not really, it wont. We shall almost never get here at all.
But then, why would this help performance?

Yes, it is not needed. I will be testing it without this
also.

thanks,

- KK