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From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: "Martin J. Bligh" <Martin.Bligh@us.ibm.com>
Cc: Andrew Morton <akpm@digeo.com>,
	William Lee Irwin III <wli@holomorphy.com>,
	Paolo Ciarrocchi <ciarrocchi@linuxmail.org>,
	linux-kernel@vger.kernel.org
Subject: Re: LMbench2.0 results
Date: 08 Sep 2002 18:07:28 +0100	[thread overview]
Message-ID: <1031504848.26888.238.camel@irongate.swansea.linux.org.uk> (raw)
In-Reply-To: <2090000.1031442267@flay>

On Sun, 2002-09-08 at 00:44, Martin J. Bligh wrote:
> >> Perhaps testing with overcommit on would be useful.
> > 
> > Well yes - the new overcommit code was a significant hit on the 16ways
> > was it not?  You have some numbers on that?
> 
> About 20% hit on system time for kernel compiles.

That suprises me a lot. On a 2 way and 4 way the 2.4 memory overcommit
check code didnt show up. That may be down to the 2 way being on a CPU
that has no measurable cost for locked operations and the 4 way being an
ancient ppro a friend has.

If it is the memory overcommit handling then there are plenty of ways to
deal with it efficiently in the non-preempt case at least. I had
wondered originally about booking chunks of pages off per CPU (take the
remaining overcommit divide by four and only when a CPU finds its
private block is empty take a lock and redistribute the remaining
allocation). Since boxes almost never get that close to overcommit
kicking in then it should mean we close to never touch a locked count.


  reply	other threads:[~2002-09-08 17:01 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2002-09-07 12:18 LMbench2.0 results Paolo Ciarrocchi
2002-09-07 12:27 ` Jeff Garzik
2002-09-07 18:53   ` Rik van Riel
2002-09-07 21:44     ` Alan Cox
2002-09-13 22:46       ` Pavel Machek
2002-09-07 14:33 ` James Morris
2002-09-09 22:22   ` Cliff White
2002-09-07 16:20 ` Andrew Morton
2002-09-07 20:03   ` William Lee Irwin III
2002-09-07 23:12     ` Andrew Morton
2002-09-07 23:01       ` William Lee Irwin III
2002-09-07 23:44       ` Martin J. Bligh
2002-09-08 17:07         ` Alan Cox [this message]
2002-09-08 18:11           ` Martin J. Bligh
2002-09-08 18:40           ` Andrew Morton
2002-09-08 20:48             ` Hugh Dickins
2002-09-08 21:51               ` Andrew Morton
2002-09-09 21:13             ` Alan Cox
2002-09-09 21:44               ` Andrew Morton
2002-09-09 22:09                 ` Alan Cox
2002-09-08  7:51     ` Andrew Morton
2002-09-08  7:37       ` David S. Miller
2002-09-08  8:28         ` William Lee Irwin III
2002-09-08  8:25           ` David S. Miller
2002-09-08  9:12             ` William Lee Irwin III
2002-09-08 20:02   ` Daniel Phillips
2002-09-09 13:37     ` Rik van Riel
2002-09-09 16:16       ` Daniel Phillips
2002-09-09 16:26         ` Martin J. Bligh
2002-09-09 16:55           ` Daniel Phillips
2002-09-09 17:24             ` Martin J. Bligh
2002-09-09 21:11             ` Alan Cox
2002-09-09 16:52         ` Andrew Morton
2002-09-07 12:40 Paolo Ciarrocchi
2002-09-07 14:09 Shane Shrybman
2002-09-07 18:04 Paolo Ciarrocchi
2002-09-13 22:49 ` Pavel Machek
2002-09-07 18:09 Paolo Ciarrocchi
2002-09-08  7:51 ` Andrew Morton
2002-09-14 18:26 Paolo Ciarrocchi
2002-09-15 18:08 ` Pavel Machek
2002-09-22 12:42 Paolo Ciarrocchi

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