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Date:   Wed, 22 Feb 2017 10:58:08 +0800
From:   Jason Wang <>
To:     "Michael S. Tsirkin" <>
Subject: Re: [PATCH net-next] virtio-net: switch to use build_skb() for small

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<>
> 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


> Acked-by: Michael S. Tsirkin<>

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