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genirq/timings: Add infrastructure for estimating the next interrupt arrival time

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An interrupt behaves with a burst of activity with periodic interval of time
followed by one or two peaks of longer interval.

As the time intervals are periodic, statistically speaking they follow a normal
distribution and each interrupts can be tracked individually.

Add a mechanism to compute the statistics on all interrupts, except the
timers which are deterministic from a prediction point of view, as their
expiry time is known.

The goal is to extract the periodicity for each interrupt, with the last
timestamp and sum them, so the next event can be predicted to a certain
extent.

Taking the earliest prediction gives the expected wakeup on the system
(assuming a timer won't expire before).

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: "Rafael J . Wysocki" <rafael@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Link: http://lkml.kernel.org/r/1498227072-5980-2-git-send-email-daniel.lezcano@linaro.org
This commit is contained in:
Daniel Lezcano 2017-06-23 16:11:08 +02:00 • committed by Thomas Gleixner
parent b2d3d61adb
commit e1c9214955
3 changed files with 359 additions and 0 deletions
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19
kernel/irq/internals.h
View file

@ -275,13 +275,21 @@ struct irq_timings {
DECLARE_PER_CPU(struct irq_timings, irq_timings);
extern void irq_timings_free(int irq);
extern int irq_timings_alloc(int irq);
static inline void irq_remove_timings(struct irq_desc *desc)
{
desc->istate &= ~IRQS_TIMINGS;
irq_timings_free(irq_desc_get_irq(desc));
}
static inline void irq_setup_timings(struct irq_desc *desc, struct irqaction *act)
{
int irq = irq_desc_get_irq(desc);
int ret;
/*
* We don't need the measurement because the idle code already
* knows the next expiry event.
@ -289,6 +297,17 @@ static inline void irq_setup_timings(struct irq_desc *desc, struct irqaction *ac
if (act->flags & __IRQF_TIMER)
return;
/*
* In case the timing allocation fails, we just want to warn,
* not fail, so letting the system boot anyway.
*/
ret = irq_timings_alloc(irq);
if (ret) {
pr_warn("Failed to allocate irq timing stats for irq%d (%d)",
irq, ret);
return;
}
desc->istate |= IRQS_TIMINGS;
}