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

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Date:	Tue, 15 Oct 2013 12:26:21 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Juri Lelli <juri.lelli@...il.com>
Cc:	Ingo Molnar <mingo@...nel.org>, 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

On Tue, Oct 15, 2013 at 12:00:20PM +0200, Juri Lelli wrote:
> On 10/14/2013 04:06 PM, Ingo Molnar wrote:
> > 
> > * Juri Lelli <juri.lelli@...il.com> wrote:
> > 
> >> +#ifdef CONFIG_SMP
> >> +		struct dl_bw *dl_b = &cpu_rq(i)->rd->dl_bw;
> >> +#else
> >> +		struct dl_bw *dl_b = &cpu_rq(i)->dl.dl_bw;
> >> +#endif
> > 
> >> +#ifdef CONFIG_SMP
> >> +		struct dl_bw *dl_b = &cpu_rq(i)->rd->dl_bw;
> >> +#else
> >> +		struct dl_bw *dl_b = &cpu_rq(i)->dl.dl_bw;
> >> +#endif
> > 
> > Btw., this kind of SMP/UP assymetry pattern really sucks. Why not make UP 
> > use the SMP data structure, even if it's degenerate?
> > 
> 
> Yes, I don't like it either, but that comes from the fact that it seemed to me
> that, semantically, bandwidth for -deadline tasks has to be associated to the
> single runqueue in UP and to the root_domain for SMP. In UP root_domain is
> compiled out, so I'm not sure to understand what you suggest. I could probably
> let dl_bw live on runqueues with the assumption that all the runqueues from the
> same root_domain have the same dl_bw, that represents the dl_bw of the
> root_domain. But I don't like this replication either :(.

#ifdef CONFIG_SMP

static inline struct dl_bw *dl_bw_of(int i)
{
	return &cpu_rq(i)->rd->dl_bw;
}

#else

static inline struct dl_bw *dl_bw_of(int i)
{
	return &cpu_rq(i)->dl.dl_bw;
}

#endif

?
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