linux-kernel - Re: [PATCH 3/3] vmevent: Implement special low-memory attribute

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Date:	Tue, 8 May 2012 01:21:47 -0700
From:	Anton Vorontsov <anton.vorontsov@...aro.org>
To:	KOSAKI Motohiro <kosaki.motohiro@...il.com>
Cc:	Pekka Enberg <penberg@...nel.org>,
	Minchan Kim <minchan@...nel.org>,
	Leonid Moiseichuk <leonid.moiseichuk@...ia.com>,
	John Stultz <john.stultz@...aro.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, linaro-kernel@...ts.linaro.org,
	patches@...aro.org, kernel-team@...roid.com
Subject: Re: [PATCH 3/3] vmevent: Implement special low-memory attribute

On Tue, May 08, 2012 at 01:13:05AM -0700, Anton Vorontsov wrote:
> On Tue, May 08, 2012 at 03:16:59AM -0400, KOSAKI Motohiro wrote:
> [...]
> > >So, feel free to call me an idiot, but please expand your points a
> > >little bit or give a link to the discussion you're referring to?
> > 
> > I don't think you are idiot. But I hope you test your patch before submitting.
> > That just don't work especially on x86. Because of, all x86 box have multiple zone
> > and summarized statistics (i.e. global_page_state() thing) don't work and can't
> > prevent oom nor swapping.
> 
> Now I think I understand you: we don't take into account that e.g. DMA
> zone is not usable by the normal allocations, and so if we're basing our
> calculations on summarized stats, it is indeed possible to get an OOM
> in such a case.

Oops. Looking into it more, I think I was wrong here: kernel will surely
use pages from the DMA zone when we have no pages in normal zones.

So, I don't see how we can get OOM in that case.

Hm.

-- 
Anton Vorontsov
Email: cbouatmailru@...il.com
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