netdev - Re: [PATCH net-next-2.6] filter: optimize accesses to ancillary data

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Message-Id: <20101221.123025.59692663.davem@davemloft.net>
Date:	Tue, 21 Dec 2010 12:30:25 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH net-next-2.6] filter: optimize accesses to ancillary
 data

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Thu, 16 Dec 2010 06:45:28 +0100

> We can translate pseudo load instructions at filter check time to
> dedicated instructions to speed up filtering and avoid one switch().
> libpcap currently uses SKF_AD_PROTOCOL, but custom filters probably use
> other ancillary accesses.
> 
> Note : I made the assertion that ancillary data was always accessed with
> BPF_LD|BPF_?|BPF_ABS instructions, not with BPF_LD|BPF_?|BPF_IND ones
> (offset given by K constant, not by K + X register)
> 
> On x86_64, this saves a few bytes of text :
> 
> # size net/core/filter.o.*
>    text	   data	    bss	    dec	    hex	filename
>    4864	      0	      0	   4864	   1300	net/core/filter.o.new
>    4944	      0	      0	   4944	   1350	net/core/filter.o.old
> 
> Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>

Applied, thanks Eric.
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