linux-kernel - Re: [PATCH 1/5] mm, page_owner: print migratetype of a page, not pageblock

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Message-ID: <20151105081955.GA26034@js1304-P5Q-DELUXE>
Date:	Thu, 5 Nov 2015 17:19:55 +0900
From:	Joonsoo Kim <iamjoonsoo.kim@....com>
To:	Vlastimil Babka <vbabka@...e.cz>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Minchan Kim <minchan@...nel.org>,
	Sasha Levin <sasha.levin@...cle.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Mel Gorman <mgorman@...e.de>
Subject: Re: [PATCH 1/5] mm, page_owner: print migratetype of a page, not
 pageblock

On Thu, Nov 05, 2015 at 09:15:01AM +0100, Vlastimil Babka wrote:
> On 11/05/2015 09:09 AM, Joonsoo Kim wrote:
> > On Wed, Nov 04, 2015 at 04:00:57PM +0100, Vlastimil Babka wrote:
> >> The information in /sys/kernel/debug/page_owner includes the migratetype
> >> declared during the page allocation via gfp_flags. This is also checked against
> >> the pageblock's migratetype, and reported as Fallback allocation if these two
> >> differ (although in fact fallback allocation is not the only reason why they
> >> can differ).
> >> 
> >> However, the migratetype actually printed is the one of the pageblock, not of
> >> the page itself, so it's the same for all pages in the pageblock. This is
> >> apparently a bug, noticed when working on other page_owner improvements. Fixed.
> > 
> > We can guess page migratetype through gfp_mask output although it isn't
> > easy task for now. But, there is no way to know pageblock migratetype.
> > I used this to know how memory is fragmented.
> 
> Ah, I see. How bout just we print both migratetypes then and remove the
> "Fallback" part, which can be trivially deduced from them (and as I noted it's
> somewhat misleading anyway)?

I'm okay with your new suggestion.

Thanks.

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