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SubjectRe: [PATCH net-next] tuntap: XDP_TX can use native XDP
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On 2018年03月15日 21:32, Michael S. Tsirkin wrote:
> On Thu, Mar 15, 2018 at 04:39:25PM +0800, Jason Wang wrote:
>>
>> On 2018年03月14日 11:37, Michael S. Tsirkin wrote:
>>>> return NULL;
>>>> case XDP_TX:
>>>> - xdp_xmit = true;
>>>> - /* fall through */
>>>> + get_page(alloc_frag->page);
>>>> + alloc_frag->offset += buflen;
>>>> + if (tun_xdp_xmit(tun->dev, &xdp))
>>>> + goto err_redirect;
>>>> + tun_xdp_flush(tun->dev);
>>> Why do we have to flush here though?
>>> It might be a good idea to document the reason in a code comment.
>>>
>> ndo_xdp_xmit() does not touch doorbell, so we need a ndo_xdp_flush() here.
>> It's the assumption of XDP API I think, so not sure it's worth to mention it
>> here.
>>
>> Thanks
> Can't one flush we called after multiple xmit calls?

We can and could be another patch on top. But I want to unify it with
the batching of XDP_REDIRECT by e.g let vhost submit more than one
packets through msg.control in sendmsg().

Thanks

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