linux-kernel - Re: [RESEND][PATCH v3 1/1] sched: Report the different kinds of imbalances in /proc/schedstat

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Date: Tue, 14 May 2024 19:53:58 +0530
From: Shrikanth Hegde <sshegde@...ux.ibm.com>
To: Chen Yu <yu.c.chen@...el.com>, Swapnil Sapkal <swapnil.sapkal@....com>
Cc: linux-kernel@...r.kernel.org, mingo@...hat.com, peterz@...radead.org,
        torvalds@...ux-foundation.org, juri.lelli@...hat.com,
        dietmar.eggemann@....com, rostedt@...dmis.org, mgorman@...e.de,
        bristot@...hat.com, vschneid@...hat.com, vincent.guittot@...aro.org,
        gautham.shenoy@....com, kprateek.nayak@....com
Subject: Re: [RESEND][PATCH v3 1/1] sched: Report the different kinds of
 imbalances in /proc/schedstat



On 5/14/24 4:44 PM, Chen Yu wrote:
> On 2024-05-14 at 04:44:45 +0000, 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>
>> ---
>>  Documentation/scheduler/sched-stats.rst | 121 ++++++++++++++----------
>>  include/linux/sched/topology.h          |   5 +-
>>  kernel/sched/fair.c                     |  21 +++-
>>  kernel/sched/stats.c                    |   7 +-
>>  4 files changed, 99 insertions(+), 55 deletions(-)
> 
> [...]
> 
>> diff --git a/kernel/sched/stats.c b/kernel/sched/stats.c
>> index 78e48f5426ee..a02bc9db2f1c 100644
>> --- a/kernel/sched/stats.c
>> +++ b/kernel/sched/stats.c
>> @@ -151,11 +151,14 @@ 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],
> 
> Do we need to increase SCHEDSTAT_VERSION to 16?

It's been increased already as part of below commit 

commit 11b0bfa5d463b17cac5bf6b94fea4921713530c3
Author: Ingo Molnar <mingo@...nel.org>
Date:   Fri Mar 8 11:58:55 2024 +0100

    sched/debug: Increase SCHEDSTAT_VERSION to 16
    
    We changed the order of definitions within 'enum cpu_idle_type',
    which changed the order of [CPU_MAX_IDLE_TYPES] columns in
    show_schedstat().


> 
> thanks,
> Chenyu