netdev - Re: [PATCH net-next] tcp: improve recv_skip_hint for tcp_zerocopy

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Message-Id: <20191013.111705.2247028003804863450.davem@davemloft.net>
Date:   Sun, 13 Oct 2019 11:17:05 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     soheil.kdev@...il.com
Cc:     netdev@...r.kernel.org, edumazet@...gle.com, soheil@...gle.com
Subject: Re: [PATCH net-next] tcp: improve recv_skip_hint for
 tcp_zerocopy_receive

From: Soheil Hassas Yeganeh <soheil.kdev@...il.com>
Date: Thu, 10 Oct 2019 23:27:02 -0400

> From: Soheil Hassas Yeganeh <soheil@...gle.com>
> 
> tcp_zerocopy_receive() rounds down the zc->length a multiple of
> PAGE_SIZE. This results in two issues:
> - tcp_zerocopy_receive sets recv_skip_hint to the length of the
>   receive queue if the zc->length input is smaller than the
>   PAGE_SIZE, even though the data in receive queue could be
>   zerocopied.
> - tcp_zerocopy_receive would set recv_skip_hint of 0, in cases
>   where we have a little bit of data after the perfectly-sized
>   packets.
> 
> To fix these issues, do not store the rounded down value in
> zc->length. Round down the length passed to zap_page_range(),
> and return min(inq, zc->length) when the zap_range is 0.
> 
> Signed-off-by: Soheil Hassas Yeganeh <soheil@...gle.com>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Applied, thank you.