linux-kernel - Re: [RFC][PATCH 9/9] cpuidle: Use local_clock

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Message-ID: <CAJZ5v0jc29fSGFzN2Yeb+xRQZ9Y0V2_Ge17YnsEG5Um9OV25uw@mail.gmail.com>
Date:   Tue, 9 May 2023 18:18:08 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     bigeasy@...utronix.de, mark.rutland@....com, maz@...nel.org,
        catalin.marinas@....com, will@...nel.org, chenhuacai@...nel.org,
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Subject: Re: [RFC][PATCH 9/9] cpuidle: Use local_clock_noinstr()

On Mon, May 8, 2023 at 11:34 PM Peter Zijlstra <peterz@...radead.org> wrote:
>
> With the introduction of local_clock_noinstr(), local_clock() itself
> is no longer marked noinstr, use the correct function.
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> ---
>  drivers/cpuidle/cpuidle.c    |    8 ++++----
>  drivers/cpuidle/poll_state.c |    4 ++--
>  2 files changed, 6 insertions(+), 6 deletions(-)
>
> --- a/drivers/cpuidle/cpuidle.c
> +++ b/drivers/cpuidle/cpuidle.c
> @@ -145,7 +145,7 @@ static noinstr void enter_s2idle_proper(
>
>         instrumentation_begin();
>
> -       time_start = ns_to_ktime(local_clock());
> +       time_start = ns_to_ktime(local_clock_noinstr());
>
>         tick_freeze();
>         /*
> @@ -169,7 +169,7 @@ static noinstr void enter_s2idle_proper(
>         tick_unfreeze();
>         start_critical_timings();
>
> -       time_end = ns_to_ktime(local_clock());
> +       time_end = ns_to_ktime(local_clock_noinstr());
>
>         dev->states_usage[index].s2idle_time += ktime_us_delta(time_end, time_start);
>         dev->states_usage[index].s2idle_usage++;
> @@ -243,7 +243,7 @@ noinstr int cpuidle_enter_state(struct c
>         sched_idle_set_state(target_state);
>
>         trace_cpu_idle(index, dev->cpu);
> -       time_start = ns_to_ktime(local_clock());
> +       time_start = ns_to_ktime(local_clock_noinstr());
>
>         stop_critical_timings();
>         if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE)) {
> @@ -276,7 +276,7 @@ noinstr int cpuidle_enter_state(struct c
>         start_critical_timings();
>
>         sched_clock_idle_wakeup_event();
> -       time_end = ns_to_ktime(local_clock());
> +       time_end = ns_to_ktime(local_clock_noinstr());
>         trace_cpu_idle(PWR_EVENT_EXIT, dev->cpu);
>
>         /* The cpu is no longer idle or about to enter idle. */
> --- a/drivers/cpuidle/poll_state.c
> +++ b/drivers/cpuidle/poll_state.c
> @@ -15,7 +15,7 @@ static int __cpuidle poll_idle(struct cp
>  {
>         u64 time_start;
>
> -       time_start = local_clock();
> +       time_start = local_clock_noinstr();
>
>         dev->poll_time_limit = false;
>
> @@ -32,7 +32,7 @@ static int __cpuidle poll_idle(struct cp
>                                 continue;
>
>                         loop_count = 0;
> -                       if (local_clock() - time_start > limit) {
> +                       if (local_clock_noinstr() - time_start > limit) {
>                                 dev->poll_time_limit = true;
>                                 break;
>                         }
>

The above LGTM, but the teo governors uses local_clock() too.  Should
it use the _noinstr() version?