From: Andi Kleen <ak@suse.de>
To: Paul Mackerras <paulus@samba.org>
Cc: Christoph Lameter <clameter@sgi.com>,
Rik van Riel <riel@redhat.com>,
Marcelo Tosatti <marcelo.tosatti@cyclades.com>,
David Woodhouse <dwmw2@infradead.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@osdl.org
Subject: Re: A scrub daemon (prezeroing)
Date: Fri, 4 Feb 2005 10:28:01 +0100 [thread overview]
Message-ID: <20050204092801.GE10347@wotan.suse.de> (raw)
In-Reply-To: <16899.15980.791820.132469@cargo.ozlabs.ibm.com>
> > advantage of all the optimizations that modern memory subsystems have for
> > linear accesses. And if hardware exists that can offload that from the cpu
> > then the cpu caches are only minimally affected.
>
> I can believe that prezeroing could provide a benefit on some
> machines, but I don't think it will provide any on ppc64.
On modern x86 clears can be done quite quickly (no memory read access) with
write combining writes. The problem is just that this will force the
page out of cache. If there is any chance that the CPU will be accessing
the data soon it's better to do the slower cached RMW clear.
-Andi
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next prev parent reply other threads:[~2005-02-04 9:28 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-01-21 20:29 Christoph Lameter
2005-01-27 12:15 ` David Woodhouse
2005-01-27 13:12 ` Robin Holt
2005-01-27 13:14 ` David Woodhouse
2005-01-27 17:02 ` Christoph Lameter
2005-02-08 11:31 ` Ralf Baechle
2005-02-02 15:32 ` Marcelo Tosatti
2005-02-02 19:05 ` Christoph Lameter
2005-02-02 16:31 ` Marcelo Tosatti
2005-02-02 21:31 ` Christoph Lameter
2005-02-02 21:39 ` David Woodhouse
2005-02-03 3:06 ` Rik van Riel
2005-02-03 23:39 ` Paul Mackerras
2005-02-04 0:59 ` Christoph Lameter
2005-02-04 5:30 ` Paul Mackerras
2005-02-04 6:26 ` Christoph Lameter
2005-02-04 6:43 ` Nick Piggin
2005-02-04 6:50 ` Christoph Lameter
2005-02-04 9:20 ` Paul Mackerras
2005-02-04 9:28 ` Andi Kleen [this message]
2005-02-04 17:02 ` Christoph Lameter
2005-02-04 22:25 ` Paul Mackerras
2005-02-02 21:00 ` Maciej W. Rozycki
2005-02-02 21:33 ` David Woodhouse
-- strict thread matches above, loose matches on Subject: below --
2005-01-04 23:13 Prezeroing V3 [1/4]: Allow request for zeroed memory Christoph Lameter
2005-01-08 21:12 ` Hugh Dickins
2005-01-08 21:56 ` David S. Miller
2005-01-21 20:15 ` A scrub daemon (prezeroing) Christoph Lameter
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