linux-kernel - Re: [PATCH v2 1/1] sched: Report the different kinds of imbalances in /proc/schedstat

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Date: Fri, 15 Mar 2024 22:26:47 +0530
From: Shrikanth Hegde <sshegde@...ux.ibm.com>
To: Swapnil Sapkal <swapnil.sapkal@....com>
Cc: 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, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/1] sched: Report the different kinds of imbalances in
 /proc/schedstat



On 3/15/24 7:25 PM, 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.
> 
> Signed-off-by: Swapnil Sapkal <swapnil.sapkal@....com>
> ---
>  Documentation/scheduler/sched-stats.rst | 119 ++++++++++++++----------
>  include/linux/sched/topology.h          |   5 +-
>  kernel/sched/fair.c                     |  21 ++++-
>  kernel/sched/stats.c                    |   7 +-
>  4 files changed, 98 insertions(+), 54 deletions(-)
> 
> diff --git a/Documentation/scheduler/sched-stats.rst b/Documentation/scheduler/sched-stats.rst
> index 7c2b16c4729d..e2a6b53a38ee 100644
> --- a/Documentation/scheduler/sched-stats.rst
> +++ b/Documentation/scheduler/sched-stats.rst
> @@ -6,10 +6,15 @@ Version 16 of schedstats changed the order of definitions within
>  'enum cpu_idle_type', which changed the order of [CPU_MAX_IDLE_TYPES]
>  columns in show_schedstat(). In particular the position of CPU_IDLE
>  and __CPU_NOT_IDLE changed places. The size of the array is unchanged.

Size of the array would change after this patch. So this line can be updated. 


> +Also stop reporting 'lb_imbalance' as it has no significance anymore
> +and instead add more relevant fields namely 'lb_imbalance_load',
> +'lb_imbalance_util', 'lb_imbalance_task' and 'lb_imbalance_misfit'.
>  

Rest of the changes look good to me. 
Reviewed-by: Shrikanth Hegde <sshegde@...ux.ibm.com>