From: Hannes Frederic Sowa <hannes@stressinduktion.org>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: netdev@vger.kernel.org, Jay Vosburgh <jay.vosburgh@canonical.com>,
Thomas Graf <tgraf@suug.ch>,
Daniel Borkmann <dborkman@redhat.com>,
Eric Dumazet <eric.dumazet@gmail.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH net-next] arch_fast_hash: avoid indirect function calls and implement hash in asm
Date: Thu, 04 Dec 2014 17:37:10 +0100 [thread overview]
Message-ID: <1417711030.5386.35.camel@localhost> (raw)
In-Reply-To: <20141204155610.GA22340@gondor.apana.org.au>
On Do, 2014-12-04 at 23:56 +0800, Herbert Xu wrote:
> 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?
Yes, jhash always beats crc32 in software on x86_64 and ia32.
Bye,
Hannes
next prev parent reply other threads:[~2014-12-04 16:37 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-12-04 13:08 [PATCH net-next] arch_fast_hash: avoid indirect function calls and implement hash in asm Hannes Frederic Sowa
2014-12-04 15:56 ` Herbert Xu
2014-12-04 16:37 ` Hannes Frederic Sowa [this message]
2014-12-04 19:27 ` Jay Vosburgh
2014-12-04 19:32 ` Hannes Frederic Sowa
2014-12-09 19:39 ` David Miller
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