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From: Peter Zijlstra <peterz@infradead.org>
To: Fabio Checconi <fchecconi@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
	Paul Turner <pjt@google.com>,
	Dario Faggioli <faggioli@gandalf.sssup.it>,
	Michael Trimarchi <michael@evidence.eu.com>,
	Dhaval Giani <dhaval@retis.sssup.it>,
	Tommaso Cucinotta <t.cucinotta@sssup.it>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/3] sched: enforce per-cpu utilization limits on runtime balancing
Date: Tue, 23 Mar 2010 21:32:04 +0100	[thread overview]
Message-ID: <1269376324.5283.6.camel@laptop> (raw)
In-Reply-To: <20100303170014.GP2490@gandalf.sssup.it>

On Wed, 2010-03-03 at 18:00 +0100, Fabio Checconi wrote:
> > From: Peter Zijlstra <peterz@infradead.org>
> > Date: Thu, Feb 25, 2010 09:28:23PM +0100
> >
> > On Tue, 2010-02-23 at 19:56 +0100, Fabio Checconi wrote:
> > > +#ifdef CONFIG_SMP
> > > +static inline unsigned long rt_init_free_bw(void)
> > > +{
> > > +       unsigned long used = to_ratio(global_rt_period(), global_rt_runtime());
> > > +
> > > +       return to_ratio(RUNTIME_INF, RUNTIME_INF) - used;
> > > +}
> > > +#endif
> > 
> > > +static void __rt_restart_balancing(void)
> > > +{
> > > +       unsigned long used, global, free;
> > > +       struct rq *rq;
> > > +       int i;
> > > +
> > > +       used = rt_used_bandwidth();
> > > +       global = to_ratio(RUNTIME_INF, RUNTIME_INF);
> > > +
> > > +       free = global - used;
> > 
> > 
> > We take the max as RUNTIME_INF instead of global_rt_* so that we can
> > move runtime around and fully saturate a single cpu (given there is
> > enough free to compensate on other cpus) ?
> 
> The only reason I've used RUNTIME_INF instead of global_rt_* is for the
> !GROUP_SCHED case, where using the global_rt_* values would make balancing
> have no effect at all (the initial value for def_rt_bandwidth already
> uses the maximum bw on each cpu) .  The current throttling implementation
> in this case still tries to concentrate bw on a single cpu, and I wanted
> to replicate the same behaviour.
> 
> Should I go for the global_rt_* values and add some #ifdef unreadability
> to avoid the balancing overhead in the !GROUP_SCHED case?


Nah, but adding a comment to clarify this might help.. I only asked
because it was not immediately obvious.


  reply	other threads:[~2010-03-23 20:32 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-02-23 18:56 [PATCH 0/3] sched: use EDF to throttle RT task groups v2 Fabio Checconi
2010-02-23 18:56 ` [PATCH 1/3] sched: use EDF to schedule groups Fabio Checconi
2010-02-25 20:28   ` Peter Zijlstra
2010-03-03 16:59     ` Fabio Checconi
2010-02-23 18:56 ` [PATCH 2/3] sched: enforce per-cpu utilization limits on runtime balancing Fabio Checconi
2010-02-25 20:28   ` Peter Zijlstra
2010-03-03 16:59     ` Fabio Checconi
2010-02-25 20:28   ` Peter Zijlstra
2010-03-03 17:00     ` Fabio Checconi
2010-03-23 20:32       ` Peter Zijlstra [this message]
2010-02-25 20:28   ` Peter Zijlstra
2010-03-03 16:59     ` Fabio Checconi
2010-02-25 20:28   ` Peter Zijlstra
2010-03-03 17:00     ` Fabio Checconi
2010-03-23 20:33       ` Peter Zijlstra
2010-02-25 20:28   ` Peter Zijlstra
2010-03-03 17:00     ` Fabio Checconi
2010-02-23 18:56 ` [PATCH 3/3] sched: make runtime balancing code more EDF-friendly Fabio Checconi
2010-02-25 20:28   ` Peter Zijlstra
2010-03-03 17:01     ` Fabio Checconi
2010-02-25 20:28 ` [PATCH 0/3] sched: use EDF to throttle RT task groups v2 Peter Zijlstra
2010-02-27 12:33 ` Peter Zijlstra
2010-03-03 17:01   ` Fabio Checconi
2010-03-23 20:30     ` Peter Zijlstra
2010-03-23 20:56       ` Dhaval Giani
2010-03-23 21:51         ` Tommaso Cucinotta

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