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

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Message-ID: <f6bd6617-b8fb-4760-a90b-ceeca6d4e415@linux.ibm.com>
Date: Thu, 28 Mar 2024 11:21:32 +0530
From: Shrikanth Hegde <sshegde@...ux.ibm.com>
To: Vitalii Bursov <vitaly@...sov.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 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?

>  	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.