linux-kernel - Re: [PATCH net-next 1/2] tcp: add TCP_ZEROCOPY

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Message-ID: <20180425152422.GB27076@infradead.org>
Date:   Wed, 25 Apr 2018 08:24:22 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     Christoph Hellwig <hch@...radead.org>,
        Eric Dumazet <edumazet@...gle.com>,
        "David S . Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>,
        Soheil Hassas Yeganeh <soheil@...gle.com>
Subject: Re: [PATCH net-next 1/2] tcp: add TCP_ZEROCOPY_RECEIVE support for
 zerocopy receive

On Wed, Apr 25, 2018 at 06:01:02AM -0700, Eric Dumazet wrote:
> Thanks Christoph
> 
> Note the high cost of zap_page_range(), needed to avoid -EBUSY being returned
> from vm_insert_page() the second time TCP_ZEROCOPY_RECEIVE is used on one VMA.
> 
> Ideally a vm_replace_page() would avoid this cost ?

No my area of expertise, I'll defer to the MM folks..