Re: [patch 2/5] cpuidle: add get_poll_time callback

From: "Rafael J. Wysocki" <rafael@kernel.org>
To: Marcelo Tosatti <mtosatti@redhat.com>
Cc: kvm-devel <kvm@vger.kernel.org>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Radim Krcmar <rkrcmar@redhat.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Wanpeng Li <kernellwp@gmail.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
	Raslan KarimAllah <karahmed@amazon.de>,
	Boris Ostrovsky <boris.ostrovsky@oracle.com>,
	Ankur Arora <ankur.a.arora@oracle.com>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	Linux PM <linux-pm@vger.kernel.org>
Subject: Re: [patch 2/5] cpuidle: add get_poll_time callback
Date: Tue, 25 Jun 2019 23:52:10 +0200	[thread overview]
Message-ID: <CAJZ5v0jk=jO2yVMDA-aNB6_DFW-zg9dBT9zxYPDDNsGa-jUYhA@mail.gmail.com> (raw)
In-Reply-To: <20190613225022.969533311@redhat.com>

On Fri, Jun 14, 2019 at 12:55 AM Marcelo Tosatti <mtosatti@redhat.com> wrote:
>
> Add a "get_poll_time" callback to the cpuidle_governor structure,
> and change poll state to poll for that amount of time.
>
> Provide a default method for it, while allowing individual governors
> to override it.
>
> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

Fair enough:

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

>
> ---
>  drivers/cpuidle/cpuidle.c    |   40 ++++++++++++++++++++++++++++++++++++++++
>  drivers/cpuidle/poll_state.c |   11 ++---------
>  include/linux/cpuidle.h      |    8 ++++++++
>  3 files changed, 50 insertions(+), 9 deletions(-)
>
> Index: linux-2.6.git/drivers/cpuidle/cpuidle.c
> ===================================================================
> --- linux-2.6.git.orig/drivers/cpuidle/cpuidle.c        2019-06-13 17:57:33.111185824 -0400
> +++ linux-2.6.git/drivers/cpuidle/cpuidle.c     2019-06-13 18:09:48.158500660 -0400
> @@ -362,6 +362,46 @@
>  }
>
>  /**
> + * cpuidle_default_poll_time - default routine used to return poll time
> + * governors can override it if necessary
> + *
> + * @drv:   the cpuidle driver tied with the cpu
> + * @dev:   the cpuidle device
> + *
> + */
> +static u64 cpuidle_default_poll_time(struct cpuidle_driver *drv,
> +                                    struct cpuidle_device *dev)
> +{
> +       int i;
> +
> +       for (i = 1; i < drv->state_count; i++) {
> +               if (drv->states[i].disabled || dev->states_usage[i].disable)
> +                       continue;
> +
> +               return (u64)drv->states[i].target_residency * NSEC_PER_USEC;
> +       }
> +
> +       return TICK_NSEC;
> +}
> +
> +/**
> + * cpuidle_get_poll_time - tell the polling driver how much time to poll,
> + *                        in nanoseconds.
> + *
> + * @drv: the cpuidle driver tied with the cpu
> + * @dev: the cpuidle device
> + *
> + */
> +u64 cpuidle_get_poll_time(struct cpuidle_driver *drv,
> +                         struct cpuidle_device *dev)
> +{
> +       if (cpuidle_curr_governor->get_poll_time)
> +               return cpuidle_curr_governor->get_poll_time(drv, dev);
> +
> +       return cpuidle_default_poll_time(drv, dev);
> +}
> +
> +/**
>   * cpuidle_install_idle_handler - installs the cpuidle idle loop handler
>   */
>  void cpuidle_install_idle_handler(void)
> Index: linux-2.6.git/drivers/cpuidle/poll_state.c
> ===================================================================
> --- linux-2.6.git.orig/drivers/cpuidle/poll_state.c     2019-06-13 17:57:33.111185824 -0400
> +++ linux-2.6.git/drivers/cpuidle/poll_state.c  2019-06-13 18:01:19.846944820 -0400
> @@ -20,16 +20,9 @@
>         local_irq_enable();
>         if (!current_set_polling_and_test()) {
>                 unsigned int loop_count = 0;
> -               u64 limit = TICK_NSEC;
> -               int i;
> +               u64 limit;
>
> -               for (i = 1; i < drv->state_count; i++) {
> -                       if (drv->states[i].disabled || dev->states_usage[i].disable)
> -                               continue;
> -
> -                       limit = (u64)drv->states[i].target_residency * NSEC_PER_USEC;
> -                       break;
> -               }
> +               limit = cpuidle_get_poll_time(drv, dev);
>
>                 while (!need_resched()) {
>                         cpu_relax();
> Index: linux-2.6.git/include/linux/cpuidle.h
> ===================================================================
> --- linux-2.6.git.orig/include/linux/cpuidle.h  2019-06-13 17:57:33.111185824 -0400
> +++ linux-2.6.git/include/linux/cpuidle.h       2019-06-13 18:01:19.846944820 -0400
> @@ -132,6 +132,8 @@
>  extern int cpuidle_enter(struct cpuidle_driver *drv,
>                          struct cpuidle_device *dev, int index);
>  extern void cpuidle_reflect(struct cpuidle_device *dev, int index);
> +extern u64 cpuidle_get_poll_time(struct cpuidle_driver *drv,
> +                                struct cpuidle_device *dev);
>
>  extern int cpuidle_register_driver(struct cpuidle_driver *drv);
>  extern struct cpuidle_driver *cpuidle_get_driver(void);
> @@ -166,6 +168,9 @@
>                                 struct cpuidle_device *dev, int index)
>  {return -ENODEV; }
>  static inline void cpuidle_reflect(struct cpuidle_device *dev, int index) { }
> +extern u64 cpuidle_get_poll_time(struct cpuidle_driver *drv,
> +                                struct cpuidle_device *dev)
> +{return 0; }
>  static inline int cpuidle_register_driver(struct cpuidle_driver *drv)
>  {return -ENODEV; }
>  static inline struct cpuidle_driver *cpuidle_get_driver(void) {return NULL; }
> @@ -246,6 +251,9 @@
>                                         struct cpuidle_device *dev,
>                                         bool *stop_tick);
>         void (*reflect)         (struct cpuidle_device *dev, int index);
> +
> +       u64 (*get_poll_time)    (struct cpuidle_driver *drv,
> +                                       struct cpuidle_device *dev);
>  };
>
>  #ifdef CONFIG_CPU_IDLE
>
>