linux-kernel - Re: additional oom-killer tuneable worth submitting?

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Message-Id: <200612081819.43991.a1426z@gawab.com>
Date:	Fri, 8 Dec 2006 18:19:43 +0300
From:	Al Boldi <a1426z@...ab.com>
To:	Alan <alan@...rguk.ukuu.org.uk>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: additional oom-killer tuneable worth submitting?

Alan wrote:
> Al Boldi <a1426z@...ab.com> wrote:
> > > That is why we have no-overcommit support.
> >
> > Alan, I think you know that this isn't really true, due to shared-libs.
>
> Shared libraries are correctly handled by no-overcommit and in fact they
> have almost zero impact on out of memory questions because the shared
> parts of the library are file backed and constant. That means they don't
> actually cost swap space.

What I understood from Arjan is that the problem isn't swapspace, but rather 
that shared-libs are implement via a COW trick, which always overcommits, no 
matter what.

> > > Now there is an argument for
> > > a meaningful rlimit-as to go with it, and together I think they do
> > > what you really need.
> >
> > The problem with rlimit is that it works per process.  Tuning this by
> > hand may be awkward and/or wasteful.  What we need is to rlimit on a
> > global basis, by calculating an upperlimit dynamically, such as to avoid
> > overcommit/OOM.
>
> You've just described the existing no overcommit functionality, although
> you've forgotten to allow for pre-reserving of stacks and some other
> detail that has been found to make it work better as it has been refined.

Are you saying there is some new no-overcommit functionality in 2.6.19, or 
has this been there before?


Thanks!

--
Al

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