Re: [PATCH 3.2.0-rc1 0/3] Used Memory Meter pseudo-device and relatedchanges in MM

From: Pekka Enberg
Date: Thu Jan 05 2012 - 07:40:53 EST


On Thu, Jan 5, 2012 at 1:47 PM, <leonid.moiseichuk@xxxxxxxxx> 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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