From: Andi Kleen <ak@suse.de>
To: Christoph Lameter <christoph@lameter.com>
Cc: Andi Kleen <ak@suse.de>, christoph <christoph@scalex86.org>,
akpm@osdl.org, linux-kernel@vger.kernel.org, shai@scalex86.org
Subject: Re: [PATCH] Move some variables into the "most_readonly" section??
Date: Wed, 15 Jun 2005 01:54:01 +0200 [thread overview]
Message-ID: <20050614235401.GW11898@wotan.suse.de> (raw)
In-Reply-To: <Pine.LNX.4.62.0506141621510.23266@graphe.net>
On Tue, Jun 14, 2005 at 04:27:55PM -0700, Christoph Lameter wrote:
> On Wed, 15 Jun 2005, Andi Kleen wrote:
>
> > > If these maps would start in the middle of a cacheline then additional
> > > cacheline fetches may become necessary to scan an array etc.
> >
> > But the CPUs do prefetching anyways for that. Do you have numbers
> > that this is actually worth it?
>
> Its not only for scanning an array. A struct may contains a lot of
> related information like for example boot_cpu_data. Aligning
> increases locality and the likelyhood that no additional cachelines have
> to be fetched.
On the other hand it will increase the overall working set so there might
be more cache misses again. It's a trade off and the outcome is not clear.
Do you have numbers?
When in doubt I would suggest the less wasteful in memory solution.
-Andi
next prev parent reply other threads:[~2005-06-14 23:54 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-06-07 19:58 christoph
2005-06-08 13:18 ` Andi Kleen
2005-06-14 22:54 ` christoph
2005-06-14 23:04 ` Andi Kleen
2005-06-14 23:17 ` Christoph Lameter
2005-06-14 23:19 ` Andi Kleen
2005-06-14 23:27 ` Christoph Lameter
2005-06-14 23:54 ` Andi Kleen [this message]
2005-06-14 23:23 ` Andrew Morton
2005-06-14 23:46 ` christoph
2005-06-14 23:58 ` Andrew Morton
2005-06-15 0:05 ` christoph
2005-06-15 0:16 ` Andrew Morton
2005-06-15 0:41 ` Andi Kleen
2005-06-17 13:55 ` Anton Blanchard
2005-06-27 23:17 ` christoph
2005-06-15 0:18 ` Nick Piggin
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