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

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Date:	Wed, 14 Jan 2009 15:45:35 +0900
From:	"MinChan Kim" <minchan.kim@...il.com>
To:	"Arve Hjønnevåg" <arve@...roid.com>,
	"Balbir Singh" <balbir@...ux.vnet.ibm.com>,
	"KOSAKI Motohiro" <kosaki.motohiro@...fujitsu.com>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Rik van Riel" <riel@...riel.com>, linux-mm <linux-mm@...ck.org>
Cc:	"Brian Swetland" <swetland@...gle.com>, "Greg KH" <greg@...ah.com>,
	arve@...gle.com, "San Mehat" <san@...roid.com>,
	"Alan Cox" <alan@...rguk.ukuu.org.uk>,
	"Robert Love" <rlove@...gle.com>, linux-kernel@...r.kernel.org
Subject: Re: lowmemory android driver not needed?

Hi, Arve.

On Wed, Jan 14, 2009 at 11:30 AM, Arve Hjønnevåg <arve@...roid.com> wrote:
> The oom killer does not kick in until all caches are emptied. Our user
> space code changes the oom_adj value of processes that are no longer
> in the foreground so that they killed first (the process saves its
> state but does not exit). To avoid excessive demand paging, the low
> memory killer will kill these processes when the memory available
> drops below a threshold.


It have some problems. (drivers/staging/android/lwmemorykiller.c)

1. lowmem_shrink function have to answer about vm's query the cache size fast.
2. it don't consider page size and memory size when it make
lowmem_minfree's values.
3. If system have many processes, for_each_process take a long time.
it may result system latency although lowmemkiller intend to avoid
latency.
4. Most important thing. Could we use memory controller instead of
lowmemkiller ? I am not sure since I don't follow up memory controller
in these days.

I think we have to use existing facility if possible.
Previously, There are similar kinds of patches. but It can't merge
mainline due to some issue.  They can comment about lowmemkiller. I
will CC them.

> --
> Arve Hjønnevåg
>
>
> On Tue, Jan 13, 2009 at 6:18 PM, Brian Swetland <swetland@...gle.com> wrote:
>>
>> Looping in Arve who wrote the low memory killer and can explain things
>> in more detail.
>>
>> Brian
>>
>> [Greg KH <greg@...ah.com>]
>>> Hi San,
>>>
>>> Alan Cox pointed me at the /proc/<pid>/oom_adj file that controls the
>>> oom-killer score for any process as being more than sufficent to control
>>> the oom killer.
>>>
>>> This makes me wonder why you wrote the android lowmemlorykiller driver?
>>>
>>> What is that driver for that is not already present in the existing
>>> oom_* values for every process?
>>>
>>> thanks,
>>>
>>> greg k-h
>> --
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-- 
Kinds regards,
MinChan Kim