linux-kernel - Re: [PATCH v2 3/6] sched: Report the different kinds of imbalances in /proc/schedstat

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Message-ID: <56790316-d73c-4201-a2fa-9be3019e2f49@linux.ibm.com>
Date: Fri, 20 Dec 2024 23:53:17 +0530
From: Shrikanth Hegde <sshegde@...ux.ibm.com>
To: Swapnil Sapkal <swapnil.sapkal@....com>
Cc: dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        mgorman@...e.de, vschneid@...hat.com, iamjoonsoo.kim@....com,
        qyousef@...alina.io, alexs@...nel.org, lukasz.luba@....com,
        gautham.shenoy@....com, kprateek.nayak@....com, ravi.bangoria@....com,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        peterz@...radead.org, mingo@...hat.com, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, corbet@....net
Subject: Re: [PATCH v2 3/6] sched: Report the different kinds of imbalances in
 /proc/schedstat



On 12/20/24 12:02, Swapnil Sapkal wrote:
> In /proc/schedstat, lb_imbalance reports the sum of imbalances
> discovered in sched domains with each call to sched_balance_rq(), which is
> not very useful because lb_imbalance does not mention whether the imbalance
> is due to load, utilization, nr_tasks or misfit_tasks. Remove this field
> from /proc/schedstat.
> 
> Currently there is no field in /proc/schedstat to report different types
> of imbalances. Introduce new fields in /proc/schedstat to report the
> total imbalances in load, utilization, nr_tasks or misfit_tasks.
> 
> Added fields to /proc/schedstat:
>          - lb_imbalance_load: Total imbalance due to load.
>          - lb_imbalance_util: Total imbalance due to utilization.
>          - lb_imbalance_task: Total imbalance due to number of tasks.
>          - lb_imbalance_misfit: Total imbalance due to misfit tasks.
> 
> Reviewed-by: Shrikanth Hegde <sshegde@...ux.ibm.com>
> Signed-off-by: Swapnil Sapkal <swapnil.sapkal@....com>

I think its better to merge patch 3 and patch 6.

> ---
>   include/linux/sched/topology.h |  5 ++++-
>   kernel/sched/fair.c            | 24 +++++++++++++++++++++++-
>   kernel/sched/stats.c           |  7 +++++--
>   3 files changed, 32 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h
> index 4237daa5ac7a..76a662e1ec24 100644
> --- a/include/linux/sched/topology.h
> +++ b/include/linux/sched/topology.h
> @@ -114,7 +114,10 @@ struct sched_domain {
>   	unsigned int lb_count[CPU_MAX_IDLE_TYPES];
>   	unsigned int lb_failed[CPU_MAX_IDLE_TYPES];
>   	unsigned int lb_balanced[CPU_MAX_IDLE_TYPES];
> -	unsigned int lb_imbalance[CPU_MAX_IDLE_TYPES];
> +	unsigned int lb_imbalance_load[CPU_MAX_IDLE_TYPES];
> +	unsigned int lb_imbalance_util[CPU_MAX_IDLE_TYPES];
> +	unsigned int lb_imbalance_task[CPU_MAX_IDLE_TYPES];
> +	unsigned int lb_imbalance_misfit[CPU_MAX_IDLE_TYPES];
>   	unsigned int lb_gained[CPU_MAX_IDLE_TYPES];
>   	unsigned int lb_hot_gained[CPU_MAX_IDLE_TYPES];
>   	unsigned int lb_nobusyg[CPU_MAX_IDLE_TYPES];
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 2ca3f098552c..5e7e4fe81648 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -11699,6 +11699,28 @@ static int should_we_balance(struct lb_env *env)
>   	return group_balance_cpu(sg) == env->dst_cpu;
>   }
>   
> +static void update_lb_imbalance_stat(struct lb_env *env, struct sched_domain *sd,
> +				     enum cpu_idle_type idle)
> +{
> +	if (!schedstat_enabled())
> +		return;
> +
> +	switch (env->migration_type) {
> +	case migrate_load:
> +		__schedstat_add(sd->lb_imbalance_load[idle], env->imbalance);
> +		break;
> +	case migrate_util:
> +		__schedstat_add(sd->lb_imbalance_util[idle], env->imbalance);
> +		break;
> +	case migrate_task:
> +		__schedstat_add(sd->lb_imbalance_task[idle], env->imbalance);
> +		break;
> +	case migrate_misfit:
> +		__schedstat_add(sd->lb_imbalance_misfit[idle], env->imbalance);
> +		break;
> +	}
> +}
> +
>   /*
>    * Check this_cpu to ensure it is balanced within domain. Attempt to move
>    * tasks if there is an imbalance.
> @@ -11749,7 +11771,7 @@ static int sched_balance_rq(int this_cpu, struct rq *this_rq,
>   
>   	WARN_ON_ONCE(busiest == env.dst_rq);
>   
> -	schedstat_add(sd->lb_imbalance[idle], env.imbalance);
> +	update_lb_imbalance_stat(&env, sd, idle);
>   
>   	env.src_cpu = busiest->cpu;
>   	env.src_rq = busiest;
> diff --git a/kernel/sched/stats.c b/kernel/sched/stats.c
> index eb0cdcd4d921..802bd9398a2e 100644
> --- a/kernel/sched/stats.c
> +++ b/kernel/sched/stats.c
> @@ -141,11 +141,14 @@ static int show_schedstat(struct seq_file *seq, void *v)
>   			seq_printf(seq, "domain%d %*pb", dcount++,
>   				   cpumask_pr_args(sched_domain_span(sd)));
>   			for (itype = 0; itype < CPU_MAX_IDLE_TYPES; itype++) {
> -				seq_printf(seq, " %u %u %u %u %u %u %u %u",
> +				seq_printf(seq, " %u %u %u %u %u %u %u %u %u %u %u",
>   				    sd->lb_count[itype],
>   				    sd->lb_balanced[itype],
>   				    sd->lb_failed[itype],
> -				    sd->lb_imbalance[itype],
> +				    sd->lb_imbalance_load[itype],
> +				    sd->lb_imbalance_util[itype],
> +				    sd->lb_imbalance_task[itype],
> +				    sd->lb_imbalance_misfit[itype],
>   				    sd->lb_gained[itype],
>   				    sd->lb_hot_gained[itype],
>   				    sd->lb_nobusyq[itype],

While you are adding this, please update the 
Documentation/scheduler/sched-stats.rst as well.