netdev - Re: [PATCH 1/2 net-next] af_unix: improve STREAM behavior with fragmented memory

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Message-Id: <20130810.011656.2120932434328303202.davem@davemloft.net>
Date:	Sat, 10 Aug 2013 01:16:56 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	rientjes@...gle.com, netdev@...r.kernel.org
Subject: Re: [PATCH 1/2 net-next] af_unix: improve STREAM behavior with
 fragmented memory

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Thu, 08 Aug 2013 14:37:32 -0700

> From: Eric Dumazet <edumazet@...gle.com>
> 
> unix_stream_sendmsg() currently uses order-2 allocations,
> and we had numerous reports this can fail.
> 
> The __GFP_REPEAT flag present in sock_alloc_send_pskb() is
> not helping.
> 
> This patch extends the work done in commit eb6a24816b247c
> ("af_unix: reduce high order page allocations) for
> datagram sockets.
> 
> This opens the possibility of zero copy IO (splice() and
> friends)
> 
> The trick is to not use skb_pull() anymore in recvmsg() path,
> and instead add a @consumed field in UNIXCB() to track amount
> of already read payload in the skb.
> 
> There is a performance regression for large sends
> because of extra page allocations that will be addressed
> in a follow-up patch, allowing sock_alloc_send_pskb()
> to attempt high order page allocations.
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Applied.
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