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Date:      Sat, 02 Jun 2012 14:03:42 +0300
From:      Andriy Gapon <avg@FreeBSD.org>
To:        Doug Barton <dougb@FreeBSD.org>
Cc:        =?ISO-8859-1?Q?Dag-Erling_Sm=F8?=@FreeBSD.org, Adrian Chadd <adrian@FreeBSD.org>, d@delphij.net, Eitan Adler <lists@eitanadler.com>, freebsd-arch@FreeBSD.org, rgrav <des@des.no>
Subject:   Re: Allow small amount of memory be mlock()'ed by unprivileged process?
Message-ID:  <4FC9F30E.4030205@FreeBSD.org>
In-Reply-To: <4FC81D9C.2080801@FreeBSD.org>
References:  <4FAC3EAB.6050303@delphij.net> <861umkurt8.fsf@ds4.des.no> <CAJ-VmokY%2Bpgcq999NHShbq-3rK3=oeWT2WY7NmTvVdXOHZJhdg@mail.gmail.com> <CAF6rxgmDW21aPJ5Mp6Tbk1z02ivw4UPhSaNEX%2BWiu7O0v13skA@mail.gmail.com> <20120517055425.GA802@infradead.org> <4FC762DD.90101@FreeBSD.org> <4FC81D9C.2080801@FreeBSD.org>

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on 01/06/2012 04:40 Doug Barton said the following:
> On 5/31/2012 5:23 AM, Andriy Gapon wrote:
>> In fact, FreeBSD also has this rlimit and there seems to be full support for it on
>> both user and kernel sides.
>> OTOH, PRIV_VM_MLOCK privilege seems to be granted only to the super-user in the
>> default configuration.  And this privilege kind of defeats the limit.
>>
>> Perhaps, we should/could kill the privilege and set the limit to a sufficiently
>> small/safe value for ordinary users?
> 
> I like this idea, but someone else in the thread (sorry, don't have it
> handy) brought up the point that we don't want the aggregate of per-user
> limits to be able to bring down the system either.


The unprivileged users can not spawn any new users on their own and there is a
limit on number of processes per user, so a system administrator should be able
to plan resource limits based on system capacity and utilization.

> So the right solution
> would seem to be a reasonable per-user limit, and a cap on the maximum
> total amount of locked pages for all unprivileged users, probably based
> on some percentage of total available memory?

I would agree for a default limit of zero even.  As long as I (as a system
administrator) am able to increase it for selected users and groups.

-- 
Andriy Gapon



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