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From: David Miller <davem@davemloft.net>
Subject: Re: [PATCH] net: avoid a pair of dst_hold()/dst_release() in
 ip_push_pending_frames()
Date: Mon, 24 Nov 2008 16:07:57 -0800 (PST)
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From: Eric Dumazet <dada1@cosmosbay.com>
Date: Mon, 24 Nov 2008 14:59:51 +0100

> We can reduce pressure on dst entry refcount that slowdown UDP transmit
> path on SMP machines. This pressure is visible on RTP servers when
> delivering content to mediagateways, especially big ones, handling
> thousand of streams. Several cpus send UDP frames to the same
> destination, hence use the same dst entry.
> 
> This patch makes ip_push_pending_frames() steal the refcount its
> callers had to take when filling inet->cork.dst.
> 
> This doesnt avoid all refcounting, but still gives speedups on SMP,
> on UDP/RAW transmit path.
> 
> Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>

Applied.