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

From: Preeti U Murthy <[email-masked]>
Date: Thu, 24 Oct 2013 09:34:08 +0530

Hi Peter,

On 10/23/2013 03:53 AM, Peter Zijlstra wrote:
> 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?

Let me give this a thought and get back.

Regards
Preeti U Murthy