linux-kernel - Re: [RFC PATCH 0/2] nohz idle time accounting cleanup

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Date: Fri, 7 Jun 2024 11:33:20 +0800
From: Ze Gao <zegao2021@...il.com>
To: Frederic Weisbecker <frederic@...nel.org>, Joel Fernandes <joel@...lfernandes.org>, 
	Thomas Gleixner <tglx@...utronix.de>, Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>
Cc: Cruz Zhao <CruzZhao@...ux.alibaba.com>, linux-kernel@...r.kernel.org, 
	Ze Gao <zegao@...cent.com>
Subject: Re: [RFC PATCH 0/2] nohz idle time accounting cleanup

Gently ping for comments on this change ;D

Thanks,
Ze

On Thu, May 30, 2024 at 8:24 PM Ze Gao <zegao2021@...il.com> wrote:
>
> Dear all,
>
> Currently we use is_idle_task(current) check to decide if we need
> to call tick_nohz_irq_enter() on irq entry but use idle_cpu() to
> decide if we need to call tick_nohz_irq_exit() on irq exit.
> and we rely this pair (which internally calls tick_nohz_stop_idle()
> and tick_nohz_start_idle() separately) to do accurate idle time
> accounting in most cases.
>
> IIUC, idle_cpu() now is mainly for scheduler and for tick user,
> we seem to ask less than what idle_cpu() gives us and the use of
> idle_cpu() here only make things complicated which can be proved
> by the introduction of sched_core_idle_cpu() for forcing idle
> time accounting.
>
> So I make this RFC to do this cleanup and make things simple again
> here and it should introduce no functional changes.
>
> Reviews welcome and please let me know if I'm being stupid
> or missing something obvious.
>
> Regards,
> Ze
>
> --
>
> Ze Gao (2):
>   timer: Use is_idle_task() check instead of idle_cpu() on irq exit
>   sched/core: Remove sched_core_idle_cpu()
>
>  include/linux/sched.h |  2 --
>  kernel/sched/core.c   | 13 -------------
>  kernel/softirq.c      |  2 +-
>  3 files changed, 1 insertion(+), 16 deletions(-)
>
> --
> 2.41.0
>