linux-kernel - Re: [PATCH] Update jhash.h with the new version of Jenkins' hash

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Message-Id: <200902121328.43749.rusty@rustcorp.com.au>
Date:	Thu, 12 Feb 2009 13:28:42 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>
Cc:	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	netfilter-devel@...r.kernel.org
Subject: Re: [PATCH] Update jhash.h with the new version of Jenkins' hash

On Wednesday 11 February 2009 20:49:20 Jozsef Kadlecsik wrote:
> Hi,
> 
> The current jhash.h implements the lookup2() hash function by Bob Jenkins. 
> However, lookup2() is outdated as Bob wrote a new hash function called 
> lookup3(). The new hash function
> 
> - mixes better than lookup2(): it passes the check that every input bit 
>   changes every output bit 50% of the time, while lookup2() failed it.
> - performs better: compiled with -O2 on Core2 Duo, lookup3() is 20-40% 
>   faster than lookup2() depending on the key length.

Hi Joszef,

My concern was that it's also bigger (and we inline it).  Performance is
pretty much a wash since we so rarely hash more than a few words.

Any stats on code size changes?
Rusty.
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