linux-kernel - Re: [PATCH 5/9] sched/balancing: Fix comments (trying to) refer to NOHZ_BALANCE

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Date: Wed, 6 Mar 2024 16:43:13 +0100
From: Vincent Guittot <vincent.guittot@...aro.org>
To: Ingo Molnar <mingo@...nel.org>
Cc: linux-kernel@...r.kernel.org, Shrikanth Hegde <sshegde@...ux.ibm.com>, 
	Peter Zijlstra <peterz@...radead.org>, Dietmar Eggemann <dietmar.eggemann@....com>, 
	Linus Torvalds <torvalds@...ux-foundation.org>, Valentin Schneider <vschneid@...hat.com>
Subject: Re: [PATCH 5/9] sched/balancing: Fix comments (trying to) refer to NOHZ_BALANCE_KICK

On Mon, 4 Mar 2024 at 10:48, Ingo Molnar <mingo@...nel.org> wrote:
>
> Fix two typos:
>
>  - There's no such thing as 'nohz_balancing_kick', the
>    flag is named 'BALANCE' and is capitalized:  NOHZ_BALANCE_KICK.
>
>  - Likewise there's no such thing as a 'pending nohz_balance_kick'
>    either, the NOHZ_BALANCE_KICK flag is all upper-case.
>
> Signed-off-by: Ingo Molnar <mingo@...nel.org>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Vincent Guittot <vincent.guittot@...aro.org>
> Cc: Dietmar Eggemann <dietmar.eggemann@....com>
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> Cc: Valentin Schneider <vschneid@...hat.com>
> ---
>  kernel/sched/fair.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 934ace69eb30..4c46bffb6a7a 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -12410,14 +12410,14 @@ static int newidle_balance(struct rq *this_rq, struct rq_flags *rf)
>
>  /*
>   * run_rebalance_domains is triggered when needed from the scheduler tick.
> - * Also triggered for nohz idle balancing (with nohz_balancing_kick set).

I think it should be nohz_balancer_kick() instead of nohz_balancing_kick


> + * Also triggered for NOHZ idle balancing (with NOHZ_BALANCE_KICK set).

In fact, this can be triggered even without NOHZ_BALANCE_KICK. Any of
the below can trigger this
  - NOHZ_BALANCE_KICK
  - NOHZ_STATS_KICK
  - NOHZ_NEXT_KICK

>   */
>  static __latent_entropy void run_rebalance_domains(struct softirq_action *h)
>  {
>         struct rq *this_rq = this_rq();
>         enum cpu_idle_type idle = this_rq->idle_balance;
>         /*
> -        * If this CPU has a pending nohz_balance_kick, then do the
> +        * If this CPU has a pending NOHZ_BALANCE_KICK, then do the
>          * balancing on behalf of the other idle CPUs whose ticks are
>          * stopped. Do nohz_idle_balance *before* rebalance_domains to
>          * give the idle CPUs a chance to load balance. Else we may
> --
> 2.40.1
>