Subject: Re: [PATCH 3/3] sched: Aggressive balance in domains whose groups share package resources

From: Peter Zijlstra <[email-masked]>
Date: Wed, 23 Oct 2013 00:23:26 +0200

On Mon, Oct 21, 2013 at 05:15:02PM +0530, Vaidyanathan Srinivasan wrote:
>  kernel/sched/fair.c |   18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 828ed97..bbcd96b 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -5165,6 +5165,8 @@ static int load_balance(int this_cpu, struct rq *this_rq,
>  {
>  	int ld_moved, cur_ld_moved, active_balance = 0;
>  	struct sched_group *group;
> +	struct sched_domain *child;
> +	int share_pkg_res = 0;
>  	struct rq *busiest;
>  	unsigned long flags;
>  	struct cpumask *cpus = __get_cpu_var(load_balance_mask);
> @@ -5190,6 +5192,10 @@ static int load_balance(int this_cpu, struct rq *this_rq,
>  
>  	schedstat_inc(sd, lb_count[idle]);
>  
> +	child = sd->child;
> +	if (child && child->flags & SD_SHARE_PKG_RESOURCES)
> +		share_pkg_res = 1;
> +
>  redo:
>  	if (!should_we_balance(&env)) {
>  		*continue_balancing = 0;
> @@ -5202,6 +5208,7 @@ redo:
>  		goto out_balanced;
>  	}
>  
> +redo_grp:
>  	busiest = find_busiest_queue(&env, group);
>  	if (!busiest) {
>  		schedstat_inc(sd, lb_nobusyq[idle]);
> @@ -5292,6 +5299,11 @@ more_balance:
>  			if (!cpumask_empty(cpus)) {
>  				env.loop = 0;
>  				env.loop_break = sched_nr_migrate_break;
> +				if (share_pkg_res &&
> +					cpumask_intersects(cpus,
> +						to_cpumask(group->cpumask)))

sched_group_cpus()

> +					goto redo_grp;
> +
>  				goto redo;
>  			}
>  			goto out_balanced;
> @@ -5318,9 +5330,15 @@ more_balance:
>  			 */
>  			if (!cpumask_test_cpu(this_cpu,
>  					tsk_cpus_allowed(busiest->curr))) {
> +				cpumask_clear_cpu(cpu_of(busiest), cpus);
>  				raw_spin_unlock_irqrestore(&busiest->lock,
>  							    flags);
>  				env.flags |= LBF_ALL_PINNED;
> +				if (share_pkg_res &&
> +					cpumask_intersects(cpus,
> +						to_cpumask(group->cpumask)))
> +					goto redo_grp;
> +
>  				goto out_one_pinned;
>  			}

Man this retry logic is getting annoying.. isn't there anything saner we
can do?