linux-kernel - RE: [PATCH 3.2.0-rc1 0/3] Used Memory Meter pseudo-device and related changes in MM

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Message-ID: <84FF21A720B0874AA94B46D76DB9826904554391@008-AM1MPN1-003.mgdnok.nokia.com>
Date:	Thu, 5 Jan 2012 13:02:23 +0000
From:	<leonid.moiseichuk@...ia.com>
To:	<penberg@...nel.org>
CC:	<gregkh@...e.de>, <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>, <cesarb@...arb.net>,
	<kamezawa.hiroyu@...fujitsu.com>, <emunson@...bm.net>,
	<aarcange@...hat.com>, <riel@...hat.com>, <mel@....ul.ie>,
	<rientjes@...gle.com>, <dima@...roid.com>, <rebecca@...roid.com>,
	<san@...gle.com>, <akpm@...ux-foundation.org>,
	<vesa.jaaskelainen@...ia.com>
Subject: RE: [PATCH 3.2.0-rc1 0/3] Used Memory Meter pseudo-device and
 related changes in MM

Well, mm/notify.c seems a bit global for me. At the first step I handle inputs from Greg and try to find less destructive approach to allocation tracking rather than page_alloc.
The issue is I know quite well my problem, so other guys who needs memory tracking has own requirements how account memory, how often notify/which granularity,  
how  many clients could be and so one. If I get some inputs I will be happy to implement them.

With Best Wishes,
Leonid


-----Original Message-----
From: penberg@...il.com [mailto:penberg@...il.com] On Behalf Of ext Pekka Enberg
Sent: 05 January, 2012 14:41
To: Moiseichuk Leonid (Nokia-MP/Helsinki)
Cc: gregkh@...e.de; linux-mm@...ck.org; linux-kernel@...r.kernel.org; cesarb@...arb.net; kamezawa.hiroyu@...fujitsu.com; emunson@...bm.net; aarcange@...hat.com; riel@...hat.com; mel@....ul.ie; rientjes@...gle.com; dima@...roid.com; rebecca@...roid.com; san@...gle.com; akpm@...ux-foundation.org; Jaaskelainen Vesa (Nokia-MP/Helsinki)
Subject: Re: [PATCH 3.2.0-rc1 0/3] Used Memory Meter pseudo-device and related changes in MM

On Thu, Jan 5, 2012 at 1:47 PM,  <leonid.moiseichuk@...ia.com> wrote:
> As I understand AOOM it wait until situation is reached bad conditions 
> which required memory reclaiming, selects application according to 
> free memory and oom_adj level and kills it.  So no intermediate levels could be checked (e.g.
> 75% usage),  nothing could be done in user-space to prevent killing, 
> no notification for case when memory becomes OK.
>
> What I try to do is to get notification in any application that memory 
> becomes low, and do something about it like stop processing data, 
> close unused pages or correctly shuts applications, daemons.  
> Application(s) might have necessity to install several notification 
> levels, so reaction could be adjusted based on current utilization 
> level per each application, not globally.

Sure. However, from VM point of view, both have the exact same
functionality: detect when we reach low memory condition (for some configurable threshold) and notify userspace or kernel subsystem about it.

That's the part I'd like to see implemented in mm/notify.c or similar.
I really don't care what Android or any other folks use it for exactly as long as the generic code is light-weight, clean, and we can reasonably assume that distros can actually enable it.
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