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Subject: Re: [PATCH 2/3] sched: enforce per-cpu utilization limits on
 runtime balancing
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,
       Fabio Checconi <fabio@gandalf.sssup.it>
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Date: Thu, 25 Feb 2010 21:28:23 +0100
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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) ?