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From: Andi Kleen <ak@suse.de>
To: David Miller <davem@davemloft.net>
Cc: dada1@cosmosbay.com, linux@horizon.com, akepner@sgi.com,
	netdev@vger.kernel.org
Subject: Re: [PATCH] NET : change layout of ehash table
Date: 09 Feb 2007 10:18:03 +0100	[thread overview]
Message-ID: <p73zm7n1ygk.fsf@bingen.suse.de> (raw)
In-Reply-To: <20070208.145632.74749802.davem@davemloft.net>

David Miller <davem@davemloft.net> writes:
> 
> I've applied this, but I _REALLY_ don't like the new multiply
> instructions that are used now in the hash indexing paths when
> CONFIG_SMP is set.
> 
> I think that's a higher cost than the memory waste.

You're serious? multiply on a modern CPU is _much_ cheaper than a cache miss
e.g. a K8 can do a arbitary 64bit multiplication in 3-7 cycles.
Any cache miss will be in the three to four digits at least.

-Andi

  reply	other threads:[~2007-02-09  8:17 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2006-12-19  8:56 [PATCH] irlan: handle out of memory errors Akinobu Mita
2006-12-19 22:47 ` Samuel Ortiz
2007-02-07  8:12   ` David Miller
2007-02-07 10:59     ` [PATCH] NET : change layout of ehash table Eric Dumazet
2007-02-08 22:56       ` David Miller
2007-02-09  9:18         ` Andi Kleen [this message]
2007-02-09  8:40           ` David Miller
2007-02-09  8:57             ` Andi Kleen
2007-02-09  9:06             ` Eric Dumazet
2007-02-09  9:15               ` David Miller
2007-02-09  9:36                 ` Eric Dumazet
2007-02-09  9:43                   ` David Miller
2007-02-09 10:10                     ` Andi Kleen
2007-02-09 17:44                     ` [PATCH] NET : UDP can use sk_hash to speedup lookups Eric Dumazet
2007-02-09 23:45                       ` David Miller

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