linux/kernel/sched/pelt.h
Vincent Guittot 91c27493e7 sched/irq: Add IRQ utilization tracking
interrupt and steal time are the only remaining activities tracked by
rt_avg. Like for sched classes, we can use PELT to track their average
utilization of the CPU. But unlike sched class, we don't track when
entering/leaving interrupt; Instead, we take into account the time spent
under interrupt context when we update rqs' clock (rq_clock_task).
This also means that we have to decay the normal context time and account
for interrupt time during the update.

That's also important to note that because:

  rq_clock == rq_clock_task + interrupt time

and rq_clock_task is used by a sched class to compute its utilization, the
util_avg of a sched class only reflects the utilization of the time spent
in normal context and not of the whole time of the CPU. The utilization of
interrupt gives an more accurate level of utilization of CPU.

The CPU utilization is:

  avg_irq + (1 - avg_irq / max capacity) * /Sum avg_rq

Most of the time, avg_irq is small and neglictible so the use of the
approximation CPU utilization = /Sum avg_rq was enough.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Morten.Rasmussen@arm.com
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: claudio@evidence.eu.com
Cc: daniel.lezcano@linaro.org
Cc: dietmar.eggemann@arm.com
Cc: joel@joelfernandes.org
Cc: juri.lelli@redhat.com
Cc: luca.abeni@santannapisa.it
Cc: patrick.bellasi@arm.com
Cc: quentin.perret@arm.com
Cc: rjw@rjwysocki.net
Cc: valentin.schneider@arm.com
Cc: viresh.kumar@linaro.org
Link: http://lkml.kernel.org/r/1530200714-4504-7-git-send-email-vincent.guittot@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2018-07-15 23:51:21 +02:00

73 lines
1.7 KiB
C

#ifdef CONFIG_SMP
int __update_load_avg_blocked_se(u64 now, int cpu, struct sched_entity *se);
int __update_load_avg_se(u64 now, int cpu, struct cfs_rq *cfs_rq, struct sched_entity *se);
int __update_load_avg_cfs_rq(u64 now, int cpu, struct cfs_rq *cfs_rq);
int update_rt_rq_load_avg(u64 now, struct rq *rq, int running);
int update_dl_rq_load_avg(u64 now, struct rq *rq, int running);
#if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
int update_irq_load_avg(struct rq *rq, u64 running);
#else
static inline int
update_irq_load_avg(struct rq *rq, u64 running)
{
return 0;
}
#endif
/*
* When a task is dequeued, its estimated utilization should not be update if
* its util_avg has not been updated at least once.
* This flag is used to synchronize util_avg updates with util_est updates.
* We map this information into the LSB bit of the utilization saved at
* dequeue time (i.e. util_est.dequeued).
*/
#define UTIL_AVG_UNCHANGED 0x1
static inline void cfs_se_util_change(struct sched_avg *avg)
{
unsigned int enqueued;
if (!sched_feat(UTIL_EST))
return;
/* Avoid store if the flag has been already set */
enqueued = avg->util_est.enqueued;
if (!(enqueued & UTIL_AVG_UNCHANGED))
return;
/* Reset flag to report util_avg has been updated */
enqueued &= ~UTIL_AVG_UNCHANGED;
WRITE_ONCE(avg->util_est.enqueued, enqueued);
}
#else
static inline int
update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
{
return 0;
}
static inline int
update_rt_rq_load_avg(u64 now, struct rq *rq, int running)
{
return 0;
}
static inline int
update_dl_rq_load_avg(u64 now, struct rq *rq, int running)
{
return 0;
}
static inline int
update_irq_load_avg(struct rq *rq, u64 running)
{
return 0;
}
#endif