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

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Message-ID: <CAKTCnzkczaSo==AJREX1LtbBeeybn3fsKS84ibbgc_FEMbedFg@mail.gmail.com>
Date:	Wed, 16 Nov 2011 15:39:39 +0530
From:	Balbir Singh <bsingharora@...il.com>
To:	Jerome Marchand <jmarchan@...hat.com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-mm@...ck.org
Subject: Re: [RFC PATCH V2] Enforce RSS+Swap rlimit

On Tue, Nov 15, 2011 at 6:40 PM, Jerome Marchand <jmarchan@...hat.com> 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.
>
> My tests show that code in do_anonymous_page() and __do_fault() indeed prevents
> processes to get more memory than the limit and I haven't seen any adverse
> effect, but so far, I have no test coverage of the code in do_wp_page(). I'm
> not sure how to test it.
>
> Signed-off-by: Jerome Marchand <jmarchan@...hat.com>

I think we need the get_mm_rss* definitions need to be revisited and
agreed upon. I am afraid it cannot be simple addition, since

1. It does not account for shared pages
2. If we enforce a limit without accounting for sharing, we might
enforce wrong limits

Balbir
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