linux-kernel - Re: [PATCH v2 7/7] mm/page_owner: correct owner information for early allocated pages

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Date:	Mon, 24 Nov 2014 12:10:17 +0900
From:	Joonsoo Kim <iamjoonsoo.kim@....com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Mel Gorman <mgorman@...e.de>, Johannes Weiner <hannes@...xchg.org>,
	Minchan Kim <minchan@...nel.org>, Dave Hansen <dave@...1.net>,
	Michal Nazarewicz <mina86@...a86.com>,
	Jungsoo Son <jungsoo.son@....com>,
	Ingo Molnar <mingo@...hat.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 7/7] mm/page_owner: correct owner information for
 early allocated pages

On Fri, Nov 21, 2014 at 03:38:41PM -0800, Andrew Morton wrote:
> On Fri, 21 Nov 2014 17:14:06 +0900 Joonsoo Kim <iamjoonsoo.kim@....com> wrote:
> 
> > Extended memory to store page owner information is initialized some time
> > later than that page allocator starts. Until initialization, many pages
> > can be allocated and they have no owner information. This make debugging
> > using page owner harder, so some fixup will be helpful.
> > 
> > This patch fix up this situation by setting fake owner information
> > immediately after page extension is initialized. Information doesn't
> > tell the right owner, but, at least, it can tell whether page is
> > allocated or not, more correctly.
> > 
> > On my testing, this patch catches 13343 early allocated pages, although
> > they are mostly allocated from page extension feature. Anyway, after then,
> > there is no page left that it is allocated and has no page owner flag.
> 
> We really should have a Documentation/vm/page_owner.txt which explains
> all this stuff, provides examples, etc.

Okay. Will do in next spin.

Thanks.
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