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Diffstat (limited to 'kernel/sched/pelt.c')
| -rw-r--r-- | kernel/sched/pelt.c | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/kernel/sched/pelt.c b/kernel/sched/pelt.c index b647d04d9c8b..b4b1ff96642f 100644 --- a/kernel/sched/pelt.c +++ b/kernel/sched/pelt.c @@ -237,6 +237,30 @@ ___update_load_sum(u64 now, struct sched_avg *sa, return 1; } +/* + * When syncing *_avg with *_sum, we must take into account the current + * position in the PELT segment otherwise the remaining part of the segment + * will be considered as idle time whereas it's not yet elapsed and this will + * generate unwanted oscillation in the range [1002..1024[. + * + * The max value of *_sum varies with the position in the time segment and is + * equals to : + * + * LOAD_AVG_MAX*y + sa->period_contrib + * + * which can be simplified into: + * + * LOAD_AVG_MAX - 1024 + sa->period_contrib + * + * because LOAD_AVG_MAX*y == LOAD_AVG_MAX-1024 + * + * The same care must be taken when a sched entity is added, updated or + * removed from a cfs_rq and we need to update sched_avg. Scheduler entities + * and the cfs rq, to which they are attached, have the same position in the + * time segment because they use the same clock. This means that we can use + * the period_contrib of cfs_rq when updating the sched_avg of a sched_entity + * if it's more convenient. + */ static __always_inline void ___update_load_avg(struct sched_avg *sa, unsigned long load) { |