linux-kernel - Re: [PATCH 2/3] sched/fair: Use HK_TYPE

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Message-ID: <ZtcLUcJvqSV3vXd2@localhost.localdomain>
Date: Tue, 3 Sep 2024 15:12:49 +0200
From: Frederic Weisbecker <frederic@...nel.org>
To: Waiman Long <longman@...hat.com>
Cc: 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>,
	Valentin Schneider <vschneid@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] sched/fair: Use HK_TYPE_SCHED housekeeping CPUs

Le Sun, Aug 18, 2024 at 07:45:19PM -0400, Waiman Long a écrit :
> As the previous commit has enabled the setting of HK_TYPE_SCHED
> housekeeping CPUs in nohz_full setup, we can now use the more aptly
> named HK_TYPE_SCHED housekeeping CPUs instead of HK_TYPE_MISC.
> 
> Signed-off-by: Waiman Long <longman@...hat.com>

Can we instead merge HK_FLAG_TICK, HK_FLAG_WQ, HK_FLAG_TIMER, HK_FLAG_RCU,
HK_FLAG_MISC and HK_FLAG_KTHREAD into a single
HK_FLAG_KERNEL_NOISE / HK_TYPE_KERNEL_NOISE ?

Thanks.

> ---
>  kernel/sched/fair.c | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 6be618110885..0350667f5ce8 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -12128,16 +12128,13 @@ static inline int on_null_domain(struct rq *rq)
>   * - When one of the busy CPUs notices that there may be an idle rebalancing
>   *   needed, they will kick the idle load balancer, which then does idle
>   *   load balancing for all the idle CPUs.
> - *
> - * - HK_TYPE_MISC CPUs are used for this task, because HK_TYPE_SCHED is not set
> - *   anywhere yet.
>   */
>  static inline int find_new_ilb(void)
>  {
>  	const struct cpumask *hk_mask;
>  	int ilb_cpu;
>  
> -	hk_mask = housekeeping_cpumask(HK_TYPE_MISC);
> +	hk_mask = housekeeping_cpumask(HK_TYPE_SCHED);
>  
>  	for_each_cpu_and(ilb_cpu, nohz.idle_cpus_mask, hk_mask) {
>  
> @@ -12155,7 +12152,7 @@ static inline int find_new_ilb(void)
>   * Kick a CPU to do the NOHZ balancing, if it is time for it, via a cross-CPU
>   * SMP function call (IPI).
>   *
> - * We pick the first idle CPU in the HK_TYPE_MISC housekeeping set (if there is one).
> + * We pick the first idle CPU in the HK_TYPE_SCHED housekeeping set (if there is one).
>   */
>  static void kick_ilb(unsigned int flags)
>  {
> -- 
> 2.43.5
>