Date: Thu, 13 Dec 2007 14:29:35 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: jens.axboe@oracle.com, liml@rtr.ca, lkml@rtr.ca, matthew@wil.cx,
       linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org,
       linux-scsi@vger.kernel.org, linux-mm@kvack.org, mel@csn.ul.ie
Subject: Re: QUEUE_FLAG_CLUSTER: not working in 2.6.24 ?
Message-Id: <20071213142935.47ff19d9.akpm@linux-foundation.org>
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On Thu, 13 Dec 2007 17:15:06 -0500
James Bottomley <James.Bottomley@HansenPartnership.com> wrote:

> 
> On Thu, 2007-12-13 at 14:02 -0800, Andrew Morton wrote:
> > On Thu, 13 Dec 2007 21:09:59 +0100
> > Jens Axboe <jens.axboe@oracle.com> wrote:
> > 
> > >
> > > OK, it's a vm issue,
> > 
> > cc linux-mm and probable culprit.
> > 
> > >  I have tens of thousand "backward" pages after a
> > > boot - IOW, bvec->bv_page is the page before bvprv->bv_page, not
> > > reverse. So it looks like that bug got reintroduced.
> > 
> > Bill Irwin fixed this a couple of years back: changed the page allocator so
> > that it mostly hands out pages in ascending physical-address order.
> > 
> > I guess we broke that, quite possibly in Mel's page allocator rework.
> > 
> > It would help if you could provide us with a simple recipe for
> > demonstrating this problem, please.
> 
> The simple way seems to be to malloc a large area, touch every page and
> then look at the physical pages assigned ... they now mostly seem to be
> descending in physical address.
> 

OIC.  -mm's /proc/pid/pagemap can be used to get the pfn's...
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