Messages in this thread | | | From | "Rafael J. Wysocki" <> | Date | Fri, 28 Jul 2023 17:36:55 +0200 | Subject | Re: [RFC][PATCH 1/3] cpuidle: Inject tick boundary state |
| |
On Fri, Jul 28, 2023 at 5:01 PM Peter Zijlstra <peterz@infradead.org> wrote: > > In order to facilitate governors that track history in idle-state > buckets (TEO) making a useful decision about NOHZ, make sure we have a > bucket that counts tick-and-longer. > > In order to be inclusive of the tick itself -- after all, if we do not > disable NOHZ we'll sleep for a full tick, the actual boundary should > be just short of a full tick. > > IOW, when registering the idle-states, add one that is always > disabled, just to have a bucket.
This extra bucket can be created in the governor itself, can't it?
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > --- > drivers/cpuidle/cpuidle.h | 2 + > drivers/cpuidle/driver.c | 48 +++++++++++++++++++++++++++++++++++++++++++++- > include/linux/cpuidle.h | 2 - > 3 files changed, 50 insertions(+), 2 deletions(-) > > --- a/drivers/cpuidle/cpuidle.h > +++ b/drivers/cpuidle/cpuidle.h > @@ -72,4 +72,6 @@ static inline void cpuidle_coupled_unreg > } > #endif > > +#define SHORT_TICK_NSEC (TICK_NSEC - TICK_NSEC/32) > + > #endif /* __DRIVER_CPUIDLE_H */ > --- a/drivers/cpuidle/driver.c > +++ b/drivers/cpuidle/driver.c > @@ -147,13 +147,37 @@ static void cpuidle_setup_broadcast_time > tick_broadcast_disable(); > } > > +static int tick_enter(struct cpuidle_device *dev, > + struct cpuidle_driver *drv, > + int index) > +{ > + return -ENODEV; > +} > + > +static void __cpuidle_state_init_tick(struct cpuidle_state *s) > +{ > + strcpy(s->name, "TICK"); > + strcpy(s->desc, "(no-op)"); > + > + s->target_residency_ns = SHORT_TICK_NSEC; > + s->target_residency = div_u64(SHORT_TICK_NSEC, NSEC_PER_USEC); > + > + s->exit_latency_ns = 0; > + s->exit_latency = 0; > + > + s->flags |= CPUIDLE_FLAG_UNUSABLE; > + > + s->enter = tick_enter; > + s->enter_s2idle = tick_enter; > +} > + > /** > * __cpuidle_driver_init - initialize the driver's internal data > * @drv: a valid pointer to a struct cpuidle_driver > */ > static void __cpuidle_driver_init(struct cpuidle_driver *drv) > { > - int i; > + int tick = 0, i; > > /* > * Use all possible CPUs as the default, because if the kernel boots > @@ -163,6 +187,9 @@ static void __cpuidle_driver_init(struct > if (!drv->cpumask) > drv->cpumask = (struct cpumask *)cpu_possible_mask; > > + if (WARN_ON_ONCE(drv->state_count >= CPUIDLE_STATE_MAX-2)) > + tick = 1; > + > for (i = 0; i < drv->state_count; i++) { > struct cpuidle_state *s = &drv->states[i]; > > @@ -192,6 +219,25 @@ static void __cpuidle_driver_init(struct > s->exit_latency_ns = 0; > else > s->exit_latency = div_u64(s->exit_latency_ns, NSEC_PER_USEC); > + > + if (!tick && s->target_residency_ns >= SHORT_TICK_NSEC) { > + tick = 1; > + > + if (s->target_residency_ns == SHORT_TICK_NSEC) > + continue; > + > + memmove(&drv->states[i+1], &drv->states[i], > + sizeof(struct cpuidle_state) * (CPUIDLE_STATE_MAX - i - 1)); > + __cpuidle_state_init_tick(s); > + drv->state_count++; > + i++; > + } > + } > + > + if (!tick) { > + struct cpuidle_state *s = &drv->states[i]; > + __cpuidle_state_init_tick(s); > + drv->state_count++; > } > } > > --- a/include/linux/cpuidle.h > +++ b/include/linux/cpuidle.h > @@ -16,7 +16,7 @@ > #include <linux/hrtimer.h> > #include <linux/context_tracking.h> > > -#define CPUIDLE_STATE_MAX 10 > +#define CPUIDLE_STATE_MAX 16 > #define CPUIDLE_NAME_LEN 16 > #define CPUIDLE_DESC_LEN 32 > > >
| |