linux-kernel - Re: [PATCH 12/14] sched: make dl_bw a sub-quota of rt

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Date:	Wed, 16 Oct 2013 11:19:01 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Juri Lelli <juri.lelli@...il.com>, tglx@...utronix.de,
	mingo@...hat.com, rostedt@...dmis.org, oleg@...hat.com,
	fweisbec@...il.com, darren@...art.com, johan.eker@...csson.com,
	p.faure@...tech.ch, linux-kernel@...r.kernel.org,
	claudio@...dence.eu.com, michael@...rulasolutions.com,
	fchecconi@...il.com, tommaso.cucinotta@...up.it,
	nicola.manica@...i.unitn.it, luca.abeni@...tn.it,
	dhaval.giani@...il.com, hgu1972@...il.com,
	paulmck@...ux.vnet.ibm.com, raistlin@...ux.it,
	insop.song@...il.com, liming.wang@...driver.com, jkacur@...hat.com,
	harald.gustafsson@...csson.com, vincent.guittot@...aro.org,
	bruce.ashfield@...driver.com--no-chain-reply-to
Subject: Re: [PATCH 12/14] sched: make dl_bw a sub-quota of rt_bw


* Peter Zijlstra <peterz@...radead.org> wrote:

> On Tue, Oct 15, 2013 at 03:11:33PM +0200, Ingo Molnar wrote:
> > The scheduler has over 800 #ifdefs or similar preprocessor directives:
> > 
> >   comet:~/tip> git grep '^#' kernel/sched/ | grep -v include | wc -l
> >   855
> > 
> > I'd like to see this simplified a bit, _especially_ before we add new 
> > complexity ...
> 
> I agree; however I also think its unfair to pile this on Juri.

Well, it's that particular ugly #ifdef that caught my eye.

> [...] Esp the avenue pushed here, which will increase UP text and 
> (runtime) data sizes, to which I think some people will still object.
> 
> There's this entire 'maker' community (aka. internet of things) now 
> using very small Linux devices. Think Raspberry-Pi, Intel Quark (however 
> much I hate Intel for shipping a new 32bit device) etc.
> 
> These people are wanting to run Linux on these tiny devices, with tiny 
> memories etc; we shouldn't make their life harder than it already is.
> 
> Also; you didn't object about the 29 new #ifdefs currently in tip.

It was the straw that broke the camel's back.

> How about we use some of the 'quality' conference time in EDI to do some 
> big code shuffles to get rid of some of them. I'm sure we can reduce the 
> number of ifdeffery by simply merging various similar blocks and maybe 
> write a few extra helper functions.
> 
> This is how kernel/sched/ got created in the first place; as a means to 
> keep the fingers busy at a conference ;-)

LOL, agreed, we can try that ;-)

Also, we can certainly merge SCHED_DEADLINE first, as long as there's a 
hard feature stop afterwards and as long as cleanups will eventually 
arrive.

Thanks,

	Ingo
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