linux-kernel - Re: [PATCH v4] Regression: sched: automated per session task groups

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Date:	Sun, 05 Dec 2010 18:15:40 +0100
From:	Mike Galbraith <efault@....de>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Nikos Chantziaras <realnc@...or.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] Regression: sched: automated per session task groups

On Sun, 2010-12-05 at 18:09 +0100, Mike Galbraith wrote:
> On Sun, 2010-12-05 at 17:59 +0100, Mike Galbraith wrote:
> > On Sun, 2010-12-05 at 15:12 +0000, Alan Cox wrote:
> > > > > As soon as you do that from the same terminal that you're going to
> > > > > launch the "make" from, you're back to total lossage.  Are you going
> > > > > to explain to a student that "oh, you need to create a new
> > > > > gnome-terminal tab and launch firefox from that"?
> > > > 
> > > > Btw, most people don't do that anymore.  They don't use terminals.  They 
> > > 
> > > Its a regression for those who do - and often have good reason to do.
> > > This is of course why you don't put policy in the kernel and the original
> > > patch was bogus anyway.
> > 
> > What is a very clear regression is a threaded app (say firefox) vs a
> > single threaded app, particularly on UP.  The per thread scheduling
> > model wins hands down there, because the scheduler very heavily favors
> > the threaded application.  Take that unfairness away, and you have an
> > undeniable regression.  Yes, it's not black and white, never is.
> 
> P.S.  You also have an obvious _progression_ from the perspective of the
> single threaded application, which may just as well be interactive.

P.P.S :)

systemd will have the same regressions/progressions.  It doesn't matter
one whit whether it's kernel/userland making policy.  If distro-X
includes either one, or neither, they are guaranteed to be wrong :)

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