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

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Message-ID: <20090115234404.GA20142@kroah.com>
Date:	Thu, 15 Jan 2009 15:44:04 -0800
From:	Greg KH <greg@...ah.com>
To:	Trilok Soni <soni.trilok@...il.com>
Cc:	Arve Hjønnevåg <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 Yrjölä <juha.yrjola@...idboot.com>,
	viktor.rosendahl@...ia.com
Subject: Re: lowmemory android driver not needed?

On Thu, Jan 15, 2009 at 07:02:48PM +0530, Trilok Soni wrote:
> Hi Greg,
> 
> On Thu, Jan 15, 2009 at 5:42 AM, Greg KH <greg@...ah.com> wrote:
> > On Wed, Jan 14, 2009 at 03:32:38PM -0800, Arve Hjønnevåg wrote:
> >> On Wed, Jan 14, 2009 at 3:17 PM, Greg KH <greg@...ah.com> wrote:
> >> >> We actually use 6 different thresholds for killing processes. I don't
> >> >> know what all the classes are, processes with a higher oom_adj value
> >> >> can be killed with less impact to the user than processes with a lower
> >> >> oom_adj value. The first few classes only affect latency when
> >> >> switching apps, but later classes stop non critical background
> >> >> services and finally the foreground app. Another reason to not kill
> >> >> every process at the same threshold is that memory may not be free
> >> >> immediately when the process is killed.
> >> >
> >> > But the lowmemorykiller android module doesn't have anything to do with
> >> > this, right?
> >> >
> >>
> >> It does. We write the thresholds to
> >> /sys/module/lowmemorykiller/parameters/adj and
> >> /sys/module/lowmemorykiller/parameters/minfree then set the oom_adj
> >> value per process. If the standard oom killer can be adjusted in a
> >> similar way, then we will not need the lowmemorykiller module.
> >
> > Great, care to document this somewhere so people like me don't get
> > confused?
> 
> 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 :)

thanks,

greg k-h
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