linux-kernel - Re: [PATCH 01/50] sched: monolithic code dump of what is being pushed upstream

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Date:	Wed, 11 Sep 2013 09:58:15 +0900
From:	Joonsoo Kim <iamjoonsoo.kim@....com>
To:	Mel Gorman <mgorman@...e.de>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Rik van Riel <riel@...hat.com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...nel.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 01/50] sched: monolithic code dump of what is being
 pushed upstream

On Tue, Sep 10, 2013 at 10:31:41AM +0100, Mel Gorman wrote:
> @@ -5045,15 +5038,50 @@ static int need_active_balance(struct lb_env *env)
>  
>  static int active_load_balance_cpu_stop(void *data);
>  
> +static int should_we_balance(struct lb_env *env)
> +{
> +	struct sched_group *sg = env->sd->groups;
> +	struct cpumask *sg_cpus, *sg_mask;
> +	int cpu, balance_cpu = -1;
> +
> +	/*
> +	 * In the newly idle case, we will allow all the cpu's
> +	 * to do the newly idle load balance.
> +	 */
> +	if (env->idle == CPU_NEWLY_IDLE)
> +		return 1;
> +
> +	sg_cpus = sched_group_cpus(sg);
> +	sg_mask = sched_group_mask(sg);
> +	/* Try to find first idle cpu */
> +	for_each_cpu_and(cpu, sg_cpus, env->cpus) {
> +		if (!cpumask_test_cpu(cpu, sg_mask) || !idle_cpu(cpu))
> +			continue;
> +
> +		balance_cpu = cpu;
> +		break;
> +	}
> +
> +	if (balance_cpu == -1)
> +		balance_cpu = group_balance_cpu(sg);
> +
> +	/*
> +	 * First idle cpu or the first cpu(busiest) in this sched group
> +	 * is eligible for doing load balancing at this and above domains.
> +	 */
> +	return balance_cpu != env->dst_cpu;
> +}
> +

Hello, Mel.

There is one mistake from me.
The last return statement in should_we_balance() should be
'return balance_cpu == env->dst_cpu'. The fix was submitted yesterday.

You can get more information on below thread.
https://lkml.org/lkml/2013/9/10/1

I think that this fix is somewhat important to scheduler's behavior,
so it may be better to update your test result with this fix.
Sorry for notifying this.

Thanks.
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