linux-kernel - Re: [PATCH net-next] virtio-net: switch to use build

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Message-ID: <35244d06-2d0d-3f2e-0cd1-43137988c869@redhat.com>
Date:   Wed, 22 Feb 2017 10:58:08 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] virtio-net: switch to use build_skb() for small
 buffer



On 2017年02月21日 22:37, Michael S. Tsirkin wrote:
> On Tue, Feb 21, 2017 at 04:46:28PM +0800, Jason Wang wrote:
>> This patch switch to use build_skb() for small buffer which can have
>> better performance for both TCP and XDP (since we can work at page
>> before skb creation). It also remove lots of XDP codes since both
>> mergeable and small buffer use page frag during refill now.
>>
>>                         Before   | After
>> XDP_DROP(xdp1) 64B  :  11.1Mpps | 14.4Mpps
>>
>> Tested with xdp1/xdp2/xdp_ip_tx_tunnel and netperf.
>>
>> Signed-off-by: Jason Wang<jasowang@...hat.com>
> Thanks!
> I had a similar patch for mergeable too, though it's trickier there
> as host has a lot of flexibility in sizing buffers.
> Looks like a good intermediate step to me.

Yes, I think it's more tricky for the case of mergeable buffer:

1) we need reserve NET_SKB_PAD + NET_IP_ALIGN for each buffer, this will 
break rx frag coalescing
2) need tailroom for skb_shinfo, so it won't work for all size of packet

Thanks

>
>
> Acked-by: Michael S. Tsirkin<mst@...hat.com>
>