Subject: Re: [PATCH net-next 2/2] virtio-net: coalesce rx frags when possible during rx

From: Jason Wang <[email-masked]>
Date: Fri, 01 Nov 2013 13:37:02 +0800

On 11/01/2013 10:13 AM, Rusty Russell wrote:
> Jason Wang <[email-masked]> writes:
>> Commit 2613af0ed18a11d5c566a81f9a6510b73180660a (virtio_net: migrate mergeable
>> rx buffers to page frag allocators) try to increase the payload/truesize for
>> MTU-sized traffic. But this will introduce the extra overhead for GSO packets
>> received because of the frag list. This commit tries to reduce this issue by
>> coalesce the possible rx frags when possible during rx. Test result shows the
>> about 15% improvement on full size GSO packet receiving (and even better than
>> commit 2613af0ed18a11d5c566a81f9a6510b73180660a).
> I don't know about the other users of skb_add_rx_frag, but should
> this coalesce-if-possible code be built into that?

There're several other users without the possibility check. And Eric
point out in do_tcp_sendpages() skb_add_rx_frag() and skb_can_coalesce()
were used separatedly which can allows us to do some other things in the
middle. So it was ok here.
> Thanks,
> Rusty.