Re: [PATCH net] macvtap: unbreak receiving of gro skb with frag list

On 10/26/2015 04:30 PM, Michael S. Tsirkin wrote:

On Mon, Oct 26, 2015 at 02:53:38PM +0800, Jason Wang wrote:

quoted

On 10/26/2015 02:09 PM, Michael S. Tsirkin wrote:

quoted

On Mon, Oct 26, 2015 at 11:15:57AM +0800, Jason Wang wrote:

quoted

On 10/23/2015 09:37 PM, Michael S. Tsirkin wrote:

quoted

On Fri, Oct 23, 2015 at 12:57:05AM -0400, Jason Wang wrote:

quoted

We don't have fraglist support in TAP_FEATURES. This will lead
software segmentation of gro skb with frag list. Fixes by having
frag list support in TAP_FEATURES.

With this patch single session of netperf receiving were restored from
about 5Gb/s to about 12Gb/s on mlx4.

Fixes a567dd6252 ("macvtap: simplify usage of tap_features")
Cc: Vlad Yasevich <redacted>
Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <redacted>

Thanks!
Does this mean we should look at re-adding NETIF_F_FRAGLIST
to virtio-net as well?

Not sure I get the point, but probably not. This is for receiving and
skb_copy_datagram_iter() can deal with frag list.

Point is:
- bridge within guest
- assigned device creating gro skbs with frag list bridged to virtio

I see, but this problem looks not specific to virtio. Most cards does
not support frag list.

These will be slower when used with a bridge then, won't they?

For forwarding, not sure. GRO has latency and cpu overhead anyway.

Anyway I can try to add the support for this.