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

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Date:   Wed, 22 Feb 2017 11:17:50 +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22日 11:06, Michael S. Tsirkin wrote:
> On Wed, Feb 22, 2017 at 10:58:08AM +0800, Jason Wang wrote:
>>
>> 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
> Have you seen my prototype?

Not yet, please give me a pointer.

>   It works with qemu in practice,
> just needs to cover a bunch of corner cases.

Sounds good, if you wish I can help to finalize it.

Thanks

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