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

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Message-ID: <20131015131133.GC2402@gmail.com>
Date:	Tue, 15 Oct 2013 15:11:33 +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 02:25:22PM +0200, Ingo Molnar wrote:
> >
> > Really, please make it _symmetric_ ...
> > 
> > Single core systems are becoming a historic curiosity, should we 
> > should justify every piece of extra complexity we add for them.
> > 
> > So I'd rather see obvious SMP code where the UP case works fine too, 
> > and _then_ maybe check a separate patch that adds the UP optimization, 
> > with (object size) numbers proving that it's worth it, etc.
> 
> That's a slightly larger task than it appears; the core scheduler code 
> they rely on with smp doesn't exist on up.
> 
> We can do this but we need to do it scheduler wide.

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 ...

Thanks,

	Ingo
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