linux-kernel - Re: lowmemory android driver not needed?

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Date:	Fri, 16 Jan 2009 20:16:51 +0900
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Paul Mundt <lethal@...ux-sh.org>, Greg KH <greg@...ah.com>,
	Trilok Soni <soni.trilok@...il.com>,
	"Arve Hj?nnev?g" <arve@...roid.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Pavel Machek <pavel@...e.cz>,
	Brian Swetland <swetland@...gle.com>, arve@...gle.com,
	San Mehat <san@...roid.com>, Robert Love <rlove@...gle.com>,
	linux-kernel@...r.kernel.org,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	Tony Lindgren <tony@...mide.com>,
	"ext Juha Yrj?l?" <juha.yrjola@...idboot.com>,
	viktor.rosendahl@...ia.com
Subject: Re: lowmemory android driver not needed?

Hi

>> > And there is one more lowmem driver developed by Nokia for Nokia 8xx
>> > tablets it seems. CCed Tony Lindgren,  Juha and Viktor.
>> >
>> > http://git.kernel.org/?p=linux/kernel/git/tmlind/linux-omap-2.6.git;a=blob;f=security/lowmem.c;h=ae78a530af39703e335ad769f1e6f097f63ec6dd;hb=HEAD
>>
>> As we can't stack LSMs, using the lsm interface for a simple memory
>> driver seems pretty wasteful :)
>>
> The heuristics and tunables are more what ended up being useful with this
> module, which could trivially be abstracted out. The focus of the lowmem
> module was mostly giving userspace an opportunity to change its behaviour,
> and to try to save critical state. I don't know how well this would map
> to the Android use cases, though.

This thread is very interesting.

As far as I know, embedded guys strong want to lowmem notification mecanism.
At least, I and my mem_notify receive multiple contact from embedded
and JavaVM developer.
 (include sun javavm engineer)

In ideal, I think linux MM should care this requirement directly.
LSM and driver notifier is easy breakable because these component
deeply depend on MM.

(eg, I developed /dev/mem_notify patch last year. but this patch don't
work on 2.6.28 because
split-lru patch series totally changed MM reclaim processing.)

Unfortunately, we don't have any consensus of memory notification requirement.
various people have various requirement. so, if I can discuss it and
we get consensus, I'm glad.
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