linux-kernel - Re: [RFC PATCH 2 1/2] sched: Nominate idle load balancer from a semi-idle package.

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Date:	Tue, 14 Apr 2009 10:32:08 -0700
From:	Randy Dunlap <randy.dunlap@...cle.com>
To:	Gautham R Shenoy <ego@...ibm.com>
CC:	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org, Balbir Singh <balbir@...ibm.com>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: [RFC PATCH 2 1/2] sched: Nominate idle load balancer from a semi-idle
 package.

Gautham R Shenoy wrote:
>  kernel/sched.c |  127 ++++++++++++++++++++++++++++++++++++++++++++++++++++----
>  1 files changed, 118 insertions(+), 9 deletions(-)
> 
> diff --git a/kernel/sched.c b/kernel/sched.c
> index 6cc1fd5..d702be7 100644
> --- a/kernel/sched.c
> +++ b/kernel/sched.c
>  
> +/**
> + * is_semi_idle_group - Checks if the given sched_group is semi-idle.
> + * @ilb_group:	group to be checked for semi-idleness
> + *
> + * Returns:	1 if the group is semi-idle. 0 otherwise.
> + *
> + * We define a sched_group to be semi idle if it has atleast one idle-CPU
> + * and atleast one non-idle CPU. This helper function checks if the given

"at least" (2x)

> + * sched_group is semi-idle or not.
> + */
> +static inline int is_semi_idle_group(struct sched_group *ilb_group)
> +{
> +	cpumask_and(nohz.ilb_grp_nohz_mask, nohz.cpu_mask,
> +					sched_group_cpus(ilb_group));
> +
> +	/*
> +	 * A sched_group is semi-idle when it has atleast one busy cpu
> +	 * and atleast one idle cpu.

"at least" (2x)

> +	 */
> +	if (cpumask_empty(nohz.ilb_grp_nohz_mask))
> +		return 0;
> +
> +	if (cpumask_equal(nohz.ilb_grp_nohz_mask, sched_group_cpus(ilb_group)))
> +		return 0;
> +
> +	return 1;
> +}


-- 
~Randy
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