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Date: Wed, 25 Apr 2018 08:24:22 -0700
From: Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH net-next 1/2] tcp: add TCP_ZEROCOPY_RECEIVE support for
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Message-ID: <20180425152422.GB27076@infradead.org>
References: <20180425052722.73022-1-edumazet@google.com>
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 <20180425062859.GA23914@infradead.org>
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To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>, Eric Dumazet <edumazet@google.com>, "David S . Miller" <davem@davemloft.net>, netdev <netdev@vger.kernel.org>, Andy Lutomirski <luto@kernel.org>, linux-kernel <linux-kernel@vger.kernel.org>, linux-mm <linux-mm@kvack.org>, Soheil Hassas Yeganeh <soheil@google.com>

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..