From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Fri, 5 Jun 2009 04:04:16 +0000 (+0000)
Subject: net: skb_shared_info optimization
X-Git-Tag: v2.6.31-rc1~330^2~121
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=042a53a9e437feaf2230dd2cadcecfae9c7bfe05;p=pandora-kernel.git

net: skb_shared_info optimization

skb_dma_unmap() is quite expensive for small packets,
because we use two different cache lines from skb_shared_info.

One to access nr_frags, one to access dma_maps[0]

Instead of dma_maps being an array of MAX_SKB_FRAGS + 1 elements,
let dma_head alone in a new dma_head field, close to nr_frags,
to reduce cache lines misses.

Tested on my dev machine (bnx2 & tg3 adapters), nice speedup !

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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