linux-kernel - Re: [RFC][PATCH 1/2] sched: Avoid placing RT threads on cores handling long softirqs

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Date:   Wed, 10 Aug 2022 19:11:40 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     John Stultz <jstultz@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     Connor O'Brien <connoro@...gle.com>,
        John Dias <joaodias@...gle.com>, Rick Yiu <rickyiu@...gle.com>,
        John Kacur <jkacur@...hat.com>,
        Qais Yousef <qais.yousef@....com>,
        Chris Redpath <chris.redpath@....com>,
        Abhijeet Dharmapurikar <adharmap@...cinc.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>, kernel-team@...roid.com,
        "J . Avila" <elavila@...gle.com>
Subject: Re: [RFC][PATCH 1/2] sched: Avoid placing RT threads on cores
 handling long softirqs



On 8/10/22 18:57, John Stultz wrote:
> diff --git a/init/Kconfig b/init/Kconfig
> index c7900e8975f1..b0dde2771314 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1278,6 +1278,17 @@ config SCHED_AUTOGROUP
>  	  desktop applications.  Task group autogeneration is currently based
>  	  upon task session.
>  
> +config RT_SOFTIRQ_OPTIMIZATION
> +       bool "Improve RT scheduling during long softirq execution"
> +       depends on ARM64
> +       depends on SMP
> +       default n
> +       help
> +         Enable an optimization which tries to avoid placing RT tasks on CPUs

Above line is indented with spaces only. :(

> +	 occupied by nonpreemptible tasks, such as a long softirq or CPUs
> +	 which may soon block preemptions, such as a CPU running a ksoftirq
> +	 thread which handles slow softirqs.

All help text lines should be indented with one tab + 2 spaces,
per Documentation/process/coding-style.rst.
(The 3 lines above have one tab + one space.)

-- 
~Randy