linux-kernel - Re: [Patch v9 7/8] sched/fair: Enable tuning of decay period

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Date:   Tue, 28 Jan 2020 15:56:57 -0800
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Thara Gopinath <thara.gopinath@...aro.org>, mingo@...hat.com,
        peterz@...radead.org, ionela.voinescu@....com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rui.zhang@...el.com, qperret@...gle.com, daniel.lezcano@...aro.org,
        viresh.kumar@...aro.org, rostedt@...dmis.org, will@...nel.org,
        catalin.marinas@....com, sudeep.holla@....com,
        juri.lelli@...hat.com, corbet@....net
Cc:     linux-kernel@...r.kernel.org, amit.kachhap@...il.com,
        javi.merino@...nel.org, amit.kucheria@...durent.com
Subject: Re: [Patch v9 7/8] sched/fair: Enable tuning of decay period

Hi,

On 1/28/20 2:36 PM, Thara Gopinath wrote:
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index e35b28e..be4147b 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -4376,6 +4376,11 @@
>  			incurs a small amount of overhead in the scheduler
>  			but is useful for debugging and performance tuning.
>  
> +	sched_thermal_decay_shift=
> +			[KNL, SMP] Set decay shift for thermal pressure signal.
> +			Format: integer between 0 and 10
> +			Default is 0.
> +

That tells an admin [or any reader] almost nothing about this kernel parameter
or what it does.  And nothing about what unit the value is in.
Does the value 0 disable this feature?

>  	skew_tick=	[KNL] Offset the periodic timer tick per cpu to mitigate
>  			xtime_lock contention on larger systems, and/or RCU lock
>  			contention on all systems with CONFIG_MAXSMP set.


thanks.
-- 
~Randy