Subject: Re: [RFC/RFT PATCH v3] sched: automated per tty task groups
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: david@lang.hm
Cc: Paul Menage <menage@google.com>, Lennart Poettering <mzxreary@0pointer.de>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Dhaval Giani <dhaval.giani@gmail.com>, Mike Galbraith <efault@gmx.de>,
        Vivek Goyal <vgoyal@redhat.com>, Oleg Nesterov <oleg@redhat.com>,
        Markus Trippelsdorf <markus@trippelsdorf.de>,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        Ingo Molnar <mingo@elte.hu>, LKML <linux-kernel@vger.kernel.org>,
        Balbir Singh <balbir@linux.vnet.ibm.com>
In-Reply-To: <alpine.DEB.2.00.1011161047060.3718@asgard.lang.hm>
References: <1289820766.16406.45.camel@maggy.simson.net>
	 <1289821590.16406.47.camel@maggy.simson.net>
	 <20101115125716.GA22422@redhat.com>
	 <1289856350.14719.135.camel@maggy.simson.net>
	 <20101116015648.GA11534@redhat.com>
	 <1289916171.5169.117.camel@maggy.simson.net>
	 <1289916683.2109.625.camel@laptop>
	 <AANLkTimun-VUNx77wJ4w7Z4io2jder=xkN5pCujPQL-a@mail.gmail.com>
	 <20101116170312.GA19327@tango.0pointer.de>
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	 <20101116181603.GC19327@tango.0pointer.de>
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	 <AANLkTik7cR_5JJWfk8SEf3Dngfe7yZvuivJ66dVDOuAk@mail.gmail.com>
	 <alpine.DEB.2.00.1011161047060.3718@asgard.lang.hm>
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Date: Tue, 16 Nov 2010 19:59:25 +0100
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On Tue, 2010-11-16 at 10:55 -0800, david@lang.hm wrote:
> On Tue, 16 Nov 2010, Paul Menage wrote:
> 
> > On Tue, Nov 16, 2010 at 10:21 AM, Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
> >>
> >> Not quite the same, you're nesting one level deeper. But the reality is,
> >> not a lot of people will change their userspace.
> >
> > That's a weak argument - not a lot of people will (explicitly) change
> > their kernel either - they'll get a fresh kernel via their distro
> > updates, as they would get userspace updates. So it's only a few
> > people (distros) that actually need to make such a change.
> 
> what is the downside of this patch going to be?
> 
> people who currently expect all the processes to compete equally will now 
> find that they no longer do so. If I am understanding this correctly, this 
> could mean that a box that was dedicated to running one application will 
> now have that application no longer dominate the system, instead it will 
> 'share equally' with the housekeeping apps on the system.
> 
> what would need to be done to revert to the prior situation?

build with: CONFIG_SCHED_AUTOGROUP=n, 
boot with: noautogroup or 
runtime: echo 0 > /proc/sysctl/kernel/sched_autogroup_enabled

(although the latter is a lazy one, it won't force existing tasks back
to the root group)
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