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Subject: Re: The IBM order relaxation patch
To: Ulrich.Weigand@de.ibm.com (Ulrich Weigand)
Date: Thu, 7 Feb 2002 00:18:47 +0000 (GMT)
Cc: zaitcev@redhat.com, linux-kernel@vger.kernel.org
In-Reply-To: <OF5FF19417.595BC760-ONC1256B58.00762715@de.ibm.com> from "Ulrich Weigand" at Feb 06, 2002 10:50:29 PM
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From: Alan Cox <alan@lxorguk.ukuu.org.uk>
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> >with a GPF flag? What they describe does not happen in an
> >interrupt context, so we can sleep.
> 
> Because nobody even *tries* to free adjacent pages to build up
> a free order-2 area.  You could wait really long ...

Without the rmap patch you can't easily do it

> rmap method could help here, because with reverse mappings we
> can at least try to free adjacent areas (because we then at least
> *know* who's using the pages).

rmap definitely makes it a real no brainer to do this at least for small
clusters of pages. Doing large chunks gets progressively harder
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