netdev - Re: [PATCH net-next] tcp: Set rcv zerocopy hint correctly if skb last frag is < PAGE

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Date:   Sun, 15 Dec 2019 11:59:40 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Arjun Roy <arjunroy.kdev@...il.com>
Cc:     davem@...emloft.net, netdev@...r.kernel.org, arjunroy@...gle.com,
        soheil@...gle.com, edumazet@...gle.com
Subject: Re: [PATCH net-next] tcp: Set rcv zerocopy hint correctly if skb last
 frag is < PAGE_SIZE.



On 12/15/19 11:22 AM, Jakub Kicinski wrote:
> On Thu, 12 Dec 2019 14:59:30 -0800, Arjun Roy wrote:
>> At present, if the last frag of paged data in a skb has < PAGE_SIZE
>> data, we compute the recv_skip_hint as being equal to the size of that
>> frag and the entire next skb.
>>
>> Instead, just return the runt frag size as the hint.
> 
> nit: this commit message doesn't really tell us why or what the effects
>      are going to be.

Right, I added a bit of explanation.

Basically we would hint the application to copy more bytes than needed.

Since zerocopy is best effort, this can target net-next

> 
>> Signed-off-by: Arjun Roy <arjunroy@...gle.com>
>> Acked-by: Soheil Hassas Yeganeh <soheil@...gle.com>
>> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> 
> WARNING: Missing Signed-off-by: line by nominal patch author 'Arjun Roy <arjunroy.kdev@...il.com>'
> 
> You gotta send it from the same address you signed it off from.

I sent a v2 on behalf of Arjun.

Thanks.