linux-kernel - Re: [PATCH 1/1] sched/fair: allow disabling newidle_balance with sched_relax_domain

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Date: Thu, 28 Mar 2024 18:19:34 +0200
From: Vitalii Bursov <vitaly@...sov.com>
To: Shrikanth Hegde <sshegde@...ux.ibm.com>
Cc: Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
 Juri Lelli <juri.lelli@...hat.com>,
 Vincent Guittot <vincent.guittot@...aro.org>,
 Dietmar Eggemann <dietmar.eggemann@....com>,
 Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>,
 Mel Gorman <mgorman@...e.de>, Daniel Bristot de Oliveira
 <bristot@...hat.com>, Valentin Schneider <vschneid@...hat.com>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] sched/fair: allow disabling newidle_balance with
 sched_relax_domain_level


On 28.03.24 07:51, Shrikanth Hegde wrote:
> 
> 
> On 3/28/24 6:00 AM, Vitalii Bursov wrote:
>> Change relax_domain_level checks so that it would be possible
>> to exclude all domains from newidle balancing.
>>
>> This matches the behavior described in the documentation:
>>   -1   no request. use system default or follow request of others.
>>    0   no search.
>>    1   search siblings (hyperthreads in a core).
>>
>> "2" enables levels 0 and 1, level_max excludes the last (level_max)
>> level, and level_max+1 includes all levels.
>>
>> Signed-off-by: Vitalii Bursov <vitaly@...sov.com>
>> ---
>>  kernel/cgroup/cpuset.c  | 2 +-
>>  kernel/sched/debug.c    | 1 +
>>  kernel/sched/topology.c | 2 +-
>>  3 files changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
>> index 4237c874871..da24187c4e0 100644
>> --- a/kernel/cgroup/cpuset.c
>> +++ b/kernel/cgroup/cpuset.c
>> @@ -2948,7 +2948,7 @@ bool current_cpuset_is_being_rebound(void)
>>  static int update_relax_domain_level(struct cpuset *cs, s64 val)
>>  {
>>  #ifdef CONFIG_SMP
>> -	if (val < -1 || val >= sched_domain_level_max)
>> +	if (val < -1 || val > sched_domain_level_max + 1)
>>  		return -EINVAL;
>>  #endif
>>  
>> diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
>> index 8d5d98a5834..8454cd4e5e1 100644
>> --- a/kernel/sched/debug.c
>> +++ b/kernel/sched/debug.c
>> @@ -423,6 +423,7 @@ static void register_sd(struct sched_domain *sd, struct dentry *parent)
>>  
>>  #undef SDM
>>  
>> +	debugfs_create_u32("level", 0444, parent, (u32 *)&sd->level);
> 
> It would be better if the level can be after group_flags since its a new addition?

I'll change the order.
Thanks

>>  	debugfs_create_file("flags", 0444, parent, &sd->flags, &sd_flags_fops);
>>  	debugfs_create_file("groups_flags", 0444, parent, &sd->groups->flags, &sd_flags_fops);
>>  }
>> diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
>> index 99ea5986038..3127c9b30af 100644
>> --- a/kernel/sched/topology.c
>> +++ b/kernel/sched/topology.c
>> @@ -1468,7 +1468,7 @@ static void set_domain_attribute(struct sched_domain *sd,
>>  	} else
>>  		request = attr->relax_domain_level;
>>  
>> -	if (sd->level > request) {
>> +	if (sd->level >= request) {
>>  		/* Turn off idle balance on this domain: */
>>  		sd->flags &= ~(SD_BALANCE_WAKE|SD_BALANCE_NEWIDLE);
>>  	}
> 
> Other than the above change looks good.