netdev - Re: [PATCH] netfilter: unfold two critical loops in ip_packet

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Message-ID: <499032A4.9090301@trash.net>
Date:	Mon, 09 Feb 2009 14:41:56 +0100
From:	Patrick McHardy <kaber@...sh.net>
To:	Andi Kleen <andi@...stfloor.org>
CC:	Eric Dumazet <dada1@...mosbay.com>,
	"David S. Miller" <davem@...emloft.net>,
	Netfilter Developers <netfilter-devel@...r.kernel.org>,
	Linux Network Development list <netdev@...r.kernel.org>
Subject: Re: [PATCH] netfilter: unfold two critical loops in ip_packet_match()

Andi Kleen wrote:
> On Fri, Jan 30, 2009 at 05:54:10PM +0100, Eric Dumazet wrote:
>> Andi Kleen a écrit :
>>> Eric Dumazet <dada1@...mosbay.com> writes:
>>>
>>>> While doing oprofile tests I noticed two loops are not properly unrolled by gcc
>>> That's because nobody passed -funroll-loops. Did you try that for
>>> that file? Likely will need -O2 too
>> I dont want to unroll all loops, only those two :)
> 
> gcc 4.4 will have a way to do that per function, but earlier
> you would need to move it to a separate file and specify
> the option only for that.
> 
> Doing so would be still a good idea compared to your
> patch because the code will be cleaner and might
> be more adaptable to future architectures
> (such manual tunings tend to outdate)


The interface name matching has shown up in profiles forever
though and we've actually already tried to optimize it IIRC.

Eric, I'm trying to keep all the *tables files synchronized,
could you send me a patch updating the other ones as well
please?
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