linux-kernel - Re: [PATCH v4] cpuidle: haltpoll: Add trace points for guest_halt_poll

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Date:   Tue, 14 Jun 2022 16:03:00 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Marcelo Tosatti <mtosatti@...hat.com>,
        Eiichi Tsukata <eiichi.tsukata@...anix.com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Joao Martins <joao.m.martins@...cle.com>
Subject: Re: [PATCH v4] cpuidle: haltpoll: Add trace points for
 guest_halt_poll_ns grow/shrink

On Mon, May 30, 2022 at 7:37 PM Marcelo Tosatti <mtosatti@...hat.com> wrote:
>
> On Fri, May 27, 2022 at 12:53:45AM +0000, Eiichi Tsukata wrote:
> > Add trace points as are implemented in KVM host halt polling.
> > This helps tune guest halt polling params.
> >
> > Signed-off-by: Eiichi Tsukata <eiichi.tsukata@...anix.com>
> > ---
> >  drivers/cpuidle/governors/haltpoll.c |  3 +++
> >  include/trace/events/power.h         | 29 ++++++++++++++++++++++++++++
> >  2 files changed, 32 insertions(+)
> >
> > diff --git a/drivers/cpuidle/governors/haltpoll.c b/drivers/cpuidle/governors/haltpoll.c
> > index cb2a96eafc02..1dff3a52917d 100644
> > --- a/drivers/cpuidle/governors/haltpoll.c
> > +++ b/drivers/cpuidle/governors/haltpoll.c
> > @@ -19,6 +19,7 @@
> >  #include <linux/sched.h>
> >  #include <linux/module.h>
> >  #include <linux/kvm_para.h>
> > +#include <trace/events/power.h>
> >
> >  static unsigned int guest_halt_poll_ns __read_mostly = 200000;
> >  module_param(guest_halt_poll_ns, uint, 0644);
> > @@ -90,6 +91,7 @@ static void adjust_poll_limit(struct cpuidle_device *dev, u64 block_ns)
> >               if (val > guest_halt_poll_ns)
> >                       val = guest_halt_poll_ns;
> >
> > +             trace_guest_halt_poll_ns_grow(val, dev->poll_limit_ns);
> >               dev->poll_limit_ns = val;
> >       } else if (block_ns > guest_halt_poll_ns &&
> >                  guest_halt_poll_allow_shrink) {
> > @@ -100,6 +102,7 @@ static void adjust_poll_limit(struct cpuidle_device *dev, u64 block_ns)
> >                       val = 0;
> >               else
> >                       val /= shrink;
> > +             trace_guest_halt_poll_ns_shrink(val, dev->poll_limit_ns);
> >               dev->poll_limit_ns = val;
> >       }
> >  }
> > diff --git a/include/trace/events/power.h b/include/trace/events/power.h
> > index af5018aa9517..c708521e4ed5 100644
> > --- a/include/trace/events/power.h
> > +++ b/include/trace/events/power.h
> > @@ -500,6 +500,35 @@ DEFINE_EVENT(dev_pm_qos_request, dev_pm_qos_remove_request,
> >
> >       TP_ARGS(name, type, new_value)
> >  );
> > +
> > +TRACE_EVENT(guest_halt_poll_ns,
> > +
> > +     TP_PROTO(bool grow, unsigned int new, unsigned int old),
> > +
> > +     TP_ARGS(grow, new, old),
> > +
> > +     TP_STRUCT__entry(
> > +             __field(bool, grow)
> > +             __field(unsigned int, new)
> > +             __field(unsigned int, old)
> > +     ),
> > +
> > +     TP_fast_assign(
> > +             __entry->grow   = grow;
> > +             __entry->new    = new;
> > +             __entry->old    = old;
> > +     ),
> > +
> > +     TP_printk("halt_poll_ns %u (%s %u)",
> > +             __entry->new,
> > +             __entry->grow ? "grow" : "shrink",
> > +             __entry->old)
> > +);
> > +
> > +#define trace_guest_halt_poll_ns_grow(new, old) \
> > +     trace_guest_halt_poll_ns(true, new, old)
> > +#define trace_guest_halt_poll_ns_shrink(new, old) \
> > +     trace_guest_halt_poll_ns(false, new, old)
> >  #endif /* _TRACE_POWER_H */
> >
> >  /* This part must be outside protection */
> > --
> > 2.36.1
> >
> >
>
> Signed-off-by: Marcelo Tosatti <mtosatti@...hat.com>

I took this as an ACK and applied the patch as 5.20 material.

Thanks!