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Message-ID: <45E8516B.5090203@austin.ibm.com>
Date: Fri, 02 Mar 2007 10:31:39 -0600
From: Joel Schopp <jschopp@...tin.ibm.com>
To: Mel Gorman <mel@....ul.ie>
CC: Bill Irwin <bill.irwin@...cle.com>, akpm@...ux-foundation.org,
npiggin@...e.de, clameter@...r.sgi.com, mingo@...e.hu,
arjan@...radead.org, torvalds@...l.org, mbligh@...igh.org,
Linux Memory Management List <linux-mm@...ck.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: The performance and behaviour of the anti-fragmentation related
patches
>> Exhibiting a workload where the list patch breaks down and the zone
>> patch rescues it might help if it's felt that the combination isn't as
>> good as lists in isolation. I'm sure one can be dredged up somewhere.
>
> I can't think of a workload that totally makes a mess out of list-based.
> However, list-based makes no guarantees on availability. If a system
> administrator knows they need between 10,000 and 100,000 huge pages and
> doesn't want to waste memory pinning too many huge pages at boot-time,
> the zone-based mechanism would be what he wanted.
From our testing with earlier versions of list based for memory hot-unplug on
pSeries machines we were able to hot-unplug huge amounts of memory after running the
nastiest workloads we could find for over a week. Without the patches we were unable
to hot-unplug anything within minutes of running the same workloads.
If something works for 99.999% of people (list based) and there is an easy way to
configure it for the other 0.001% of the people ("zone" based) I call that a great
solution. I really don't understand what the resistance is to these patches.
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