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

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Message-ID: <5bf73d21c03d4a642eb81de35544a4d6cfa9294c.camel@redhat.com>
Date:   Sat, 17 Dec 2022 02:04:03 -0300
From:   Leonardo Brás <leobras@...hat.com>
To:     Frederic Weisbecker <frederic@...nel.org>
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 Tue, 2022-11-29 at 12:54 +0100, Frederic Weisbecker wrote:
> 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 */

Both updated, thanks!

Out of curiosity, what does 'Unbound' means in this context?

> 
> > +	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!

Done, done, done, done.
Thanks a lot for reviewing!

Best regards,
Leo

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