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

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Message-ID: <20151026102928-mutt-send-email-mst@redhat.com>
Date:	Mon, 26 Oct 2015 10:30:22 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Jason Wang <jasowang@...hat.com>
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	Vlad Yasevich <vyasevic@...hat.com>
Subject: Re: [PATCH net] macvtap: unbreak receiving of gro skb with frag list

On Mon, Oct 26, 2015 at 02:53:38PM +0800, Jason Wang wrote:
> 
> 
> On 10/26/2015 02:09 PM, Michael S. Tsirkin wrote:
> > On Mon, Oct 26, 2015 at 11:15:57AM +0800, Jason Wang wrote:
> >>
> >> On 10/23/2015 09:37 PM, Michael S. Tsirkin wrote:
> >>> On Fri, Oct 23, 2015 at 12:57:05AM -0400, Jason Wang wrote:
> >>>> 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 <vyasevic@...hat.com>
> >>>> Cc: Michael S. Tsirkin <mst@...hat.com>
> >>>> Signed-off-by: Jason Wang <jasowang@...hat.com>
> >>> 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?

-- 
MST
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