Re: [PATCH 07/10] sched, fair: Optimize find_busiest_queue()

[Preeti U Murthy <preeti@linux.vnet.ibm.com>]

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