linux-kernel - Re: [PATCH v2 2/4] sched/isolation: Improve documentation

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Date:   Tue, 29 Nov 2022 12:54:39 +0100
From:   Frederic Weisbecker <frederic@...nel.org>
To:     Leonardo Bras <leobras@...hat.com>
Cc:     Steffen Klassert <steffen.klassert@...unet.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>,
        Tejun Heo <tj@...nel.org>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, Phil Auld <pauld@...hat.com>,
        Antoine Tenart <atenart@...nel.org>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Wang Yufen <wangyufen@...wei.com>, mtosatti@...hat.com,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pci@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH v2 2/4] sched/isolation: Improve documentation

On Thu, Oct 13, 2022 at 03:40:27PM -0300, Leonardo Bras wrote:
> Improve documentation on housekeeping types and what to expect from
> housekeeping functions.
> 
> Signed-off-by: Leonardo Bras <leobras@...hat.com>
> ---
>  include/linux/sched/isolation.h | 25 ++++++++++++++++---------
>  1 file changed, 16 insertions(+), 9 deletions(-)
> 
> diff --git a/include/linux/sched/isolation.h b/include/linux/sched/isolation.h
> index 762701f295d1c..9333c28153a7a 100644
> --- a/include/linux/sched/isolation.h
> +++ b/include/linux/sched/isolation.h
> @@ -7,18 +7,25 @@
>  #include <linux/tick.h>
>  
>  enum hk_type {
> -	HK_TYPE_TIMER,
> -	HK_TYPE_RCU,
> -	HK_TYPE_MISC,
> -	HK_TYPE_SCHED,
> -	HK_TYPE_TICK,
> -	HK_TYPE_DOMAIN,
> -	HK_TYPE_WQ,
> -	HK_TYPE_MANAGED_IRQ,
> -	HK_TYPE_KTHREAD,
> +	HK_TYPE_TIMER,		/* Timer interrupt, watchdogs */

More precisely:

     /* Unbound timer callbacks */

> +	HK_TYPE_RCU,		/* RCU callbacks */

More generally, because it's more than just about callbacks:

     /* Unbound RCU work */

> +	HK_TYPE_MISC,		/* Minor housekeeping categories */
> +	HK_TYPE_SCHED,		/* Scheduling and idle load balancing */
> +	HK_TYPE_TICK,		/* See isolcpus=nohz boot parameter */

Yes or nohz_full=

> +	HK_TYPE_DOMAIN,		/* See isolcpus=domain boot parameter*/
> +	HK_TYPE_WQ,		/* Work Queues*/

  /* Unbound workqueues */

> +	HK_TYPE_MANAGED_IRQ,	/* See isolcpus=managed_irq boot parameter */
> +	HK_TYPE_KTHREAD,	/* kernel threads */

  /* Unbound kernel threads */


>  	HK_TYPE_MAX
>  };
>  
> +/* Kernel parameters like nohz_full and isolcpus allow passing cpu numbers
> + * for disabling housekeeping types.
> + *
> + * The functions bellow work the opposite way, by referencing which cpus
> + * are able to perform the housekeeping type in parameter.
> + */

*below

Thanks!

> +
>  #ifdef CONFIG_CPU_ISOLATION
>  DECLARE_STATIC_KEY_FALSE(housekeeping_overridden);
>  int housekeeping_any_cpu(enum hk_type type);
> -- 
> 2.38.0
>