linux-kernel - Re: [PATCH] Reserve N process to root

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Date:	Fri, 12 Oct 2007 21:34:36 -0400
From:	Gustavo Chain <g@...f.cl>
To:	Al Boldi <a1426z@...ab.com>
Cc:	LKML Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Reserve N process to root

El Fri, 12 Oct 2007 09:29:10 +0300
Al Boldi <a1426z@...ab.com> escribió:

> Kyle Moffett wrote:
> > On Oct 12, 2007, at 01:37:23, Al Boldi wrote:
> > > You have a point, and resource-controllers can probably control
> > > DoS a lot better, but the they also incur more overhead.  Think
> > > of this "lockout prevention" patch as a near zero overhead safety
> > > valve.
> >
> > But why do you need to add "lockout prevention" if it already
> > exists?
> 
> I said this before, but I'll say it again: it's about overhead!
> 
> > With CFS' extremely efficient per-user-scheduling (hopefully
> > soon to be the default) there are only two forms of lockout by non-
> > root processes:  (1) Running out of PIDs in the box's PID-space
> > (think tens or hundreds of thousands of processes), or (2) Swap-
> > storming the box to death.  To put it bluntly trying to reserve free
> > PID slots is attacking the wrong end of the problem and your so
> > called "lockout prevention" could very easily ensure that 10 PIDs
> > are available even if the user has swapstormed the box with the
> > PIDs he does have.
> 
> I think you are reading this wrong.  It's not about reserving PIDs,
> it's about exceeding the max-threads limit.  This limit is global and
> affects every user including root, which is good, as this allows the
> sysadmin to fence the system into a controllable state.  So once the
> system reaches the fence, sysadmin-intervention allows root to exceed
> the fence.
> 
> Again, this is much nicer with real resource-controllers, but again
> it's also more overhead.

Just an _if()_ ?

may be enable it as an option in kernel config ?

> 
> Thanks!
> 
> --
> Al
> 
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-- 
Gustavo Chaín Dumit
Alumno de Ingeniería de Ejecución Informática
Pontificia Universidad Católica de Valparaiso
http://aleph.homeunix.com/~gchain
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