linux-kernel - Re: [RFC PATCH V2] Enforce RSS+Swap rlimit

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Date:	Wed, 16 Nov 2011 10:40:33 +0100
From:	Jerome Marchand <jmarchan@...hat.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
CC:	bsingharora@...il.com, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [RFC PATCH V2] Enforce RSS+Swap rlimit

On 11/16/2011 01:02 AM, KOSAKI Motohiro wrote:
> On 11/15/2011 8:10 AM, Jerome Marchand wrote:
>>
>> Change since V1: rebase on 3.2-rc1
>>
>> Currently RSS rlimit is not enforced. We can not forbid a process to exceeds
>> its RSS limit and allow it swap out. That would hurts the performance of all
>> system, even when memory resources are plentiful.
>>
>> Therefore, instead of enforcing a limit on rss usage alone, this patch enforces
>> a limit on rss+swap value. This is similar to memsw limits of cgroup.
>> If a process rss+swap usage exceeds RLIMIT_RSS max limit, he received a SIGBUS
>> signal. 
> 
> No good idea.
>  - RLIMIT_RSS has clear definition and this patch break it. you should makes
>    another rlimit at least.

I couldn't decide if we needed a new rlimit or not. I shall admit that I chose
the lazy option. If that's a problem, I can add a new rlimit, RLIMIT_MEMSW for
instance.

>  - SIGBUS can be ignored. rlimit shouldn't ignorable.

The SIGBUS can be ignored, not the rlimit: if RLIMIT_RSS is exceeded, the process
does not the memory it requested. The SIGBUS is here to notify the process that
something wrong has happened.

Thanks,
Jerome
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