linux-kernel - Re: [PATCH 08/15] mm: mmzone: MIGRATE

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Message-ID: <20120130145230.GQ25268@csn.ul.ie>
Date:	Mon, 30 Jan 2012 14:52:30 +0000
From:	Mel Gorman <mel@....ul.ie>
To:	Michal Nazarewicz <mina86@...a86.com>
Cc:	Marek Szyprowski <m.szyprowski@...sung.com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-media@...r.kernel.org, linux-mm@...ck.org,
	linaro-mm-sig@...ts.linaro.org,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Russell King <linux@....linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Daniel Walker <dwalker@...eaurora.org>,
	Arnd Bergmann <arnd@...db.de>,
	Jesse Barker <jesse.barker@...aro.org>,
	Jonathan Corbet <corbet@....net>,
	Shariq Hasnain <shariq.hasnain@...aro.org>,
	Chunsang Jeong <chunsang.jeong@...aro.org>,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	Benjamin Gaignard <benjamin.gaignard@...aro.org>
Subject: Re: [PATCH 08/15] mm: mmzone: MIGRATE_CMA migration type added

On Mon, Jan 30, 2012 at 02:06:50PM +0100, Michal Nazarewicz wrote:
> >>@@ -1017,11 +1049,14 @@ __rmqueue_fallback(struct zone *zone, int order, int start_migratetype)
> >> 			rmv_page_order(page);
> >>
> >> 			/* Take ownership for orders >= pageblock_order */
> >>-			if (current_order >= pageblock_order)
> >>+			if (current_order >= pageblock_order &&
> >>+			    !is_pageblock_cma(page))
> >> 				change_pageblock_range(page, current_order,
> >> 							start_migratetype);
> >>
> >>-			expand(zone, page, order, current_order, area, migratetype);
> >>+			expand(zone, page, order, current_order, area,
> >>+			       is_migrate_cma(start_migratetype)
> >>+			     ? start_migratetype : migratetype);
> >>
> >
> >What is this check meant to be doing?
> >
> >start_migratetype is determined by allocflags_to_migratetype() and
> >that never will be MIGRATE_CMA so is_migrate_cma(start_migratetype)
> >should always be false.
> 
> Right, thanks!  This should be the other way around, ie.:
> 
> +			expand(zone, page, order, current_order, area,
> +			       is_migrate_cma(migratetype)
> +			     ? migratetype : start_migratetype);
> 
> I'll fix this and the calls to is_pageblock_cma().
> 

That makes a lot more sense. Thanks.

I have a vague recollection that there was a problem with finding
unmovable pages in MIGRATE_CMA regions. This might have been part of
the problem.

-- 
Mel Gorman
SUSE Labs
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