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: <CAOJsxLEdTMB6JtYViRJq5gZ4_w5aaV18S3q-1rOXGzaMtmiW6A@mail.gmail.com>
Date:	Thu, 5 Jan 2012 14:40:49 +0200
From:	Pekka Enberg <penberg@...nel.org>
To:	leonid.moiseichuk@...ia.com
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

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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