Message-ID: <5217194B.2020209@linux.vnet.ibm.com>
Date: Fri, 23 Aug 2013 13:41:55 +0530
From: Preeti U Murthy <preeti@linux.vnet.ibm.com>
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To: Peter Zijlstra <peterz@infradead.org>
CC: Ingo Molnar <mingo@kernel.org>, Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        linux-kernel@vger.kernel.org, Mike Galbraith <efault@gmx.de>,
        Paul Turner <pjt@google.com>, Alex Shi <alex.shi@intel.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Morten Rasmussen <morten.rasmussen@arm.com>,
        Namhyung Kim <namhyung@kernel.org>, Lei Wen <leiwen@marvell.com>,
        Rik van Riel <riel@surriel.com>, Joonsoo Kim <js1304@gmail.com>
Subject: Re: [PATCH 07/10] sched, fair: Optimize find_busiest_queue()
References: <20130819160058.539049611@infradead.org> <20130819160425.527872672@infradead.org>
In-Reply-To: <20130819160425.527872672@infradead.org>
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Hi Peter,

On 08/19/2013 09:31 PM, Peter Zijlstra wrote:

In the load balancing code, looks to me that
cpumask_copy(cpus, cpu_active_mask) is not updating the env.cpus at all,
before calling find_busiest_group(). Am I missing something?

Should not cpumask_copy() below be before we update the env.cpus parameter?

static int load_balance(int this_cpu, struct rq *this_rq,
			struct sched_domain *sd, enum cpu_idle_type idle,
			int *balance)
{
	int ld_moved, cur_ld_moved, active_balance = 0;
	struct sched_group *group;
	struct rq *busiest;
	unsigned long flags;
	struct cpumask *cpus = __get_cpu_var(load_balance_mask);

	struct lb_env env = {
		.sd		= sd,
		.dst_cpu	= this_cpu,
		.dst_rq		= this_rq,
		.dst_grpmask    = sched_group_cpus(sd->groups),
		.idle		= idle,
		.loop_break	= sched_nr_migrate_break,
		.cpus		= cpus,
	};

	/*
	 * For NEWLY_IDLE load_balancing, we don't need to consider
	 * other cpus in our group
	 */
	if (idle == CPU_NEWLY_IDLE)
		env.dst_grpmask = NULL;

	cpumask_copy(cpus, cpu_active_mask);

	schedstat_inc(sd, lb_count[idle]);
redo:
	group = find_busiest_group(&env, balance);

Regards
Preeti U Murthy

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