From: Eric Dumazet <edumazet@google.com>
Date: Thu, 8 Aug 2013 21:37:32 +0000 (-0700)
Subject: af_unix: improve STREAM behavior with fragmented memory
X-Git-Tag: v3.12-rc1~132^2~307
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e370a7236321773245c5522d8bb299380830d3b2;p=pandora-kernel.git

af_unix: improve STREAM behavior with fragmented memory

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@google.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

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