linux-kernel - Re: Android low memory killer vs. memory pressure notifications

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Message-ID: <4EF132EA.7000300@am.sony.com>
Date:	Tue, 20 Dec 2011 17:14:18 -0800
From:	Frank Rowand <frank.rowand@...sony.com>
To:	Anton Vorontsov <anton.vorontsov@...aro.org>
CC:	David Rientjes <rientjes@...gle.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Michal Hocko <mhocko@...e.cz>,
	Arve Hjønnevåg <arve@...roid.com>,
	Rik van Riel <riel@...hat.com>, Pavel Machek <pavel@....cz>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	John Stultz <john.stultz@...aro.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Johannes Weiner <hannes@...xchg.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>, <tbird20d@...il.com>
Subject: Re: Android low memory killer vs. memory pressure notifications

On 12/20/11 16:28, Anton Vorontsov wrote:
> On Tue, Dec 20, 2011 at 01:36:00PM -0800, David Rientjes wrote:
>> On Tue, 20 Dec 2011, Anton Vorontsov wrote:
>>
>>> Hm, assuming that metadata is no longer an issue, why do you think avoiding
>>> cgroups would be a good idea?
>>>
>>
>> It's helpful for certain end users, particularly those in the embedded 
>> world, to be able to disable as many config options as possible to reduce 
>> the size of kernel image as much as possible, so they'll want a minimal 
>> amount of kernel functionality that allows such notifications.  Keep in 
>> mind that CONFIG_CGROUP_MEM_RES_CTLR is not enabled by default because of 
>> this (enabling it, CONFIG_RESOURCE_COUNTERS, and CONFIG_CGROUPS increases 
>> the size of the kernel text by ~1%),
> 
> So for 2MB kernel that's about 20KB of an additional text... This seems
> affordable, especially as a trade-off for the things that cgroups may
> provide.

A comment from http://lkml.indiana.edu/hypermail/linux/kernel/1102.1/00412.html:

"I care about 5K. (But honestly, I don't actively hunt stuff less than
10K in size, because there's too many of them to chase, currently)."

> 
> The fact is, for desktop and server Linux, cgroups slowly becomes a
> mandatory thing. And the reason for this is that cgroups mechanism
> provides some very useful features (in an extensible way, like plugins),
> i.e. a way to manage and track processes and its resources -- which is the
> main purpose of cgroups.

And for embedded and for real-time, some of us do not want cgroups to be
a mandatory thing.  We want it to remain configurable.  My personal
interest is in keeping the latency of certain critical paths (especially
in the scheduler) short and consistent.

-Frank

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