linux-kernel - Re: [RFC/RFT PATCH v3] sched: automated per tty task groups

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Message-ID: <20101116200356.GA27235@tango.0pointer.de>
Date:	Tue, 16 Nov 2010 21:03:56 +0100
From:	Lennart Poettering <mzxreary@...inter.de>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Dhaval Giani <dhaval.giani@...il.com>,
	Mike Galbraith <efault@....de>,
	Vivek Goyal <vgoyal@...hat.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Markus Trippelsdorf <markus@...ppelsdorf.de>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>
Subject: Re: [RFC/RFT PATCH v3] sched: automated per tty task groups

On Tue, 16.11.10 19:21, Peter Zijlstra (a.p.zijlstra@...llo.nl) wrote:

> 
> On Tue, 2010-11-16 at 19:16 +0100, Lennart Poettering wrote:
> > On Tue, 16.11.10 09:11, Linus Torvalds (torvalds@...ux-foundation.org) wrote:
> > 
> > > 
> > > On Tue, Nov 16, 2010 at 9:03 AM, Lennart Poettering
> > > <mzxreary@...inter.de> wrote:
> > > >
> > > > Binding something like this to TTYs is just backwards.
> > > 
> > > Numbers talk, bullshit walks.
> > > 
> > > The numbers have been quoted. The clear interactive behavior has been seen.
> > 
> > Here's my super-complex patch btw, to achieve exactly the same thing
> > from userspace without involving any kernel or systemd patching and
> > kernel-side logic. Simply edit your own ~/.bashrc and add this to the end:
> > 
> >   if [ "$PS1" ] ; then  
> >           mkdir -m 0700 /sys/fs/cgroup/cpu/user/$$
> >           echo $$ > /sys/fs/cgroup/cpu/user/$$/tasks
> >   fi
> > 
> > Then, as the superuser do this:
> > 
> >   mount -t cgroup cgroup /sys/fs/cgroup/cpu -o cpu
> >   mkdir -m 0777 /sys/fs/cgroup/cpu/user
> > 
> > Done. Same effect. However: not crazy.
> > 
> > I am not sure I myself will find the time to prep some 'numbers' for
> > you. They'd be the same as with the kernel patch anyway. But I am sure
> > somebody else will do it for you...
> 
> Not quite the same, you're nesting one level deeper. But the reality is,
> not a lot of people will change their userspace. 

Well, remove the 'user' part of the path and you have the exact same behaviour.

Userspace usually gets updated way more frequently in most distributions
than the kernel is. Maybe *you* never update userspace. But well, you
are not the examplary Linux user, are you?

Lennart

-- 
Lennart Poettering - Red Hat, Inc.
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