linux-kernel - Re: CMA and zone watermarks

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Message-ID: <20121009031023.GF13817@bbox>
Date:	Tue, 9 Oct 2012 12:10:23 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Rabin Vincent <rabin@....in>
Cc:	Marek Szyprowski <m.szyprowski@...sung.com>, linux-mm@...ck.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: CMA and zone watermarks

Hello,

On Mon, Oct 08, 2012 at 05:41:14PM +0200, Rabin Vincent wrote:
> It appears that when CMA is enabled, the zone watermarks are not properly
> respected, leading to for example GFP_NOWAIT allocations getting access to the
> high pools.
> 
> I ran the following test code which simply allocates pages with GFP_NOWAIT
> until it fails, and then tries GFP_ATOMIC.  Without CMA, the GFP_ATOMIC
> allocation succeeds, with CMA, it fails too.

Good spot. By wrong zone_watermark_check, it can consume reserved memory pool.

> 
> Logs attached (includes my patch which prints the migration type in the failure
> message http://marc.info/?l=linux-mm&m=134971041701306&w=2), taken on 3.6
> kernel.
> 

Fortunately, recently, Bart sent a patch about that.
http://marc.info/?l=linux-mm&m=134763299016693&w=2

Could you test above patches in your kernel?
You have to apply [2/4], [3/4], [4/4] and don't need [1/4].

Thanks.

-- 
Kind regards,
Minchan Kim
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