netdev - Re: [PATCH net-next] arch_fast_hash: avoid indirect function calls and implement hash in asm

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Message-ID: <20141204155610.GA22340@gondor.apana.org.au>
Date:	Thu, 4 Dec 2014 23:56:11 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Hannes Frederic Sowa <hannes@...essinduktion.org>
Cc:	netdev@...r.kernel.org, Jay Vosburgh <jay.vosburgh@...onical.com>,
	Thomas Graf <tgraf@...g.ch>,
	Daniel Borkmann <dborkman@...hat.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next] arch_fast_hash: avoid indirect function calls
 and implement hash in asm

On Thu, Dec 04, 2014 at 02:08:50PM +0100, Hannes Frederic Sowa wrote:
> By default the arch_fast_hash hashing function pointers are initialized
> to jhash(2). If during boot-up a CPU with SSE4.2 is detected they get
> updated to the CRC32 ones. This dispatching scheme incurs a function
> pointer lookup and indirect call for every hashing operation.

Just curious, is jhash actually faster than generic C CRC32 on
common platforms?

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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