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

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Message-Id: <20141121153841.c15fa400fd5c76d3946523a8@linux-foundation.org>
Date:	Fri, 21 Nov 2014 15:38:41 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>
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, 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.
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