From: Stephen Hemminger <shemminger@linux-foundation.org>
To: David Miller <davem@davemloft.net>
Cc: dada1@cosmosbay.com, andi@firstfloor.org, rick.jones2@hp.com,
netdev@vger.kernel.org
Subject: Re: bridge: faster compare for link local addresses
Date: Tue, 13 Mar 2007 13:06:54 -0700 [thread overview]
Message-ID: <20070313130654.7addde2b@freekitty> (raw)
In-Reply-To: <20070313.123954.21595557.davem@davemloft.net>
On Tue, 13 Mar 2007 12:39:54 -0700 (PDT)
David Miller <davem@davemloft.net> wrote:
> From: Eric Dumazet <dada1@cosmosbay.com>
> Date: Tue, 13 Mar 2007 14:38:32 +0100
>
> > But memcmp() has a strong semantic (in libc). memcmp(a, b, 6) should
> > do 6 byte compares and conditional branches, regardless of a/b
> > alignment. Or use the x86 "rep cmpsb" instruction that basically
> > has the same cost.
>
> Yep, that's the issue, gcc won't make the reductions necessary
> here to get it down to one comparison and one branch.
Also, for our usage we only care about equality, not greater/less than
return value.
--
Stephen Hemminger <shemminger@linux-foundation.org>
prev parent reply other threads:[~2007-03-13 20:07 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-03-12 23:20 bridge: faster compare for link local addresses Stephen Hemminger
2007-03-12 23:26 ` David Miller
2007-03-13 0:05 ` Rick Jones
2007-03-13 0:10 ` David Miller
2007-03-13 14:01 ` Andi Kleen
2007-03-13 13:38 ` Eric Dumazet
2007-03-13 19:39 ` David Miller
2007-03-13 20:06 ` Stephen Hemminger [this message]
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