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

[<leonid.moiseichuk@nokia.com>]

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@gmail.com [mailto:penberg@gmail.com] On Behalf Of ext Pekka Enberg
Sent: 05 January, 2012 14:41
To: Moiseichuk Leonid (Nokia-MP/Helsinki)
Cc: gregkh@suse.de; linux-mm@kvack.org; linux-kernel@vger.kernel.org; cesarb@cesarb.net; kamezawa.hiroyu@jp.fujitsu.com; emunson@mgebm.net; aarcange@redhat.com; riel@redhat.com; mel@csn.ul.ie; rientjes@google.com; dima@android.com; rebecca@android.com; san@google.com; akpm@linux-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@nokia.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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