linux-kernel - Re: [Linaro-mm-sig] [PATCH 11/15] mm: trigger page reclaim in alloc_contig

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Date:	Wed, 8 Feb 2012 11:26:40 -0800
From:	sandeep patil <psandeep.s@...il.com>
To:	Michal Nazarewicz <mina86@...a86.com>
Cc:	Mel Gorman <mel@....ul.ie>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Ohad Ben-Cohen <ohad@...ery.com>,
	Daniel Walker <dwalker@...eaurora.org>,
	Russell King <linux@....linux.org.uk>,
	Arnd Bergmann <arnd@...db.de>,
	Jesse Barker <jesse.barker@...aro.org>,
	Jonathan Corbet <corbet@....net>, linux-kernel@...r.kernel.org,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	linaro-mm-sig@...ts.linaro.org, linux-mm@...ck.org,
	Kyungmin Park <kyungmin.park@...sung.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rob Clark <rob.clark@...aro.org>,
	linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org
Subject: Re: [Linaro-mm-sig] [PATCH 11/15] mm: trigger page reclaim in
 alloc_contig_range() to stabilize watermarks

2012/2/8 Michal Nazarewicz <mina86@...a86.com>:
> On Wed, 08 Feb 2012 03:04:18 +0100, sandeep patil <psandeep.s@...il.com>
> wrote:
>>
>> There's another problem I am facing with zone watermarks and CMA.
>>
>> Test details:
>> Memory  : 480 MB of total memory, 128 MB CMA region
>> Test case : around 600 MB of file transfer over USB RNDIS onto target
>> System Load : ftpd with console running on target.
>> No one is doing CMA allocations except for the DMA allocations done by the
>> drivers.
>>
>> Result : After about 300MB transfer, I start getting GFP_ATOMIC
>> allocation failures.  This only happens if CMA region is reserved.
>> Total memory available is way above the zone watermarks. So, we ended
>> up starving
>> UNMOVABLE/RECLAIMABLE atomic allocations that cannot fallback on CMA
>> region.
>
>
> This looks like something Mel warned me about.  I don't really have a good
> solution for that yet. ;/

What if we have NR_FREE_CMA_PAGES in vmstat and use them to calculate
__zone_watermark_ok()?
However, it still doesn't solve the problem when we DON'T want to use
NR_FREE_CMA_PAGES in case of MOVABLE allocations.


Sandeep
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