Messages in this thread | | | From | Rusty Russell <> | Subject | Re: [PATCHv2 11/14] virtio: don't delay avail index update | Date | Sat, 21 May 2011 11:56:32 +0930 |
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On Fri, 20 May 2011 02:12:19 +0300, "Michael S. Tsirkin" <mst@redhat.com> wrote: > Update avail index immediately instead of upon kick: > for virtio-net RX this helps parallelism with the host. > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com> > --- > drivers/virtio/virtio_ring.c | 28 +++++++++++++++++++--------- > 1 files changed, 19 insertions(+), 9 deletions(-) > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > index eed5f29..8218fe6 100644 > --- a/drivers/virtio/virtio_ring.c > +++ b/drivers/virtio/virtio_ring.c > @@ -89,7 +89,7 @@ struct vring_virtqueue > unsigned int num_free; > /* Head of free buffer list. */ > unsigned int free_head; > - /* Number we've added since last sync. */ > + /* Number we've added since last kick. */ > unsigned int num_added;
I always like to see obsolescent nomenclature cleaned up like this. Thanks.
> /* Last used index we've seen. */ > @@ -174,6 +174,13 @@ int virtqueue_add_buf_gfp(struct virtqueue *_vq, > > BUG_ON(data == NULL); > > + /* Prevent drivers from adding more than num bufs without a kick. */ > + if (vq->num_added == vq->vring.num) { > + printk(KERN_ERR "gaaa!!!\n"); > + END_USE(vq); > + return -ENOSPC; > + } > +
I like "gaaa!" but it won't tell us which driver. How about the more conventional:
if (WARN_ON(vq->num_added >= vq->vring.num)) { END_USE(vq); return -ENOSPC; }
I'd really like to see the results of this patch. It's useless for outgoing net traffic (we deal with one packet at a time) but perhaps a flood of incoming packets would show something.
Thanks, Rusty.
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