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From: Ze Gao <zegao2021@gmail.com>
Date: Fri, 7 Jun 2024 11:33:20 +0800
Message-ID: <CAD8CoPCgzcrJ369HzanbsBWze6f44FQYy4ofmKh073yrv0Ceuw@mail.gmail.com>
Subject: Re: [RFC PATCH 0/2] nohz idle time accounting cleanup
To: Frederic Weisbecker <frederic@kernel.org>, Joel Fernandes <joel@joelfernandes.org>, 
	Thomas Gleixner <tglx@linutronix.de>, Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@elte.hu>
Cc: Cruz Zhao <CruzZhao@linux.alibaba.com>, linux-kernel@vger.kernel.org, 
	Ze Gao <zegao@tencent.com>
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Gently ping for comments on this change ;D

Thanks,
Ze

On Thu, May 30, 2024 at 8:24=E2=80=AFPM Ze Gao <zegao2021@gmail.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
>