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Message-ID: <5faddecb-af6b-4ac7-9385-8ba6539b8398@linux.ibm.com>
Date: Sat, 21 Dec 2024 00:48:06 +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 23:53, Shrikanth Hegde wrote:
>
>
> 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.
Please ignore this comment. Since there is change in patch 5 which
affects the docs, it is better patch 6 stays separate. Sorry for the noise.
>
>> ---
>> 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.
Please ignore this comment.
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