linux-kernel - Re: + memory-hotplug-exclude-isolated-page-from-pco-page-alloc.patch added to -mm tree

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Message-ID: <20090630010302.GD21254@sli10-desk.sh.intel.com>
Date:	Tue, 30 Jun 2009 09:03:02 +0800
From:	Shaohua Li <shaohua.li@...el.com>
To:	Christoph Lameter <cl@...ux-foundation.org>
Cc:	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	"mel@....ul.ie" <mel@....ul.ie>,
	"Zhao, Yakui" <yakui.zhao@...el.com>
Subject: Re: +
	memory-hotplug-exclude-isolated-page-from-pco-page-alloc.patch
	added to -mm tree

On Tue, Jun 30, 2009 at 06:20:00AM +0800, Christoph Lameter wrote:
> On Mon, 29 Jun 2009, akpm@...ux-foundation.org wrote:
> 
> > Pages marked as isolated should not be allocated again.  If such pages
> > reside in pcp list, they can be allocated too, so there is a ping-pong
> > memory offline frees some pages to pcp list and the pages get allocated
> > and then memory offline frees them again, this loop will happen again and
> > again.
> 
> Isolated pages are freed? Could they not be kept on a separate
> list with refcount elevated until the isolation procedure is complete?
Yes, they can be freed and add into pcp list. Moving them to a separate list
is feasible, but the approach is more intrusive to me. As I explained in the
patch, adding check in buffered_rmqueue() should hasn't impact for normal path.

Thanks,
Shaohua
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