Messages in this thread | | | From | cee1 <> | Date | Thu, 15 Jun 2017 22:25:49 +0800 | Subject | What is the math behind sched_avg_update()? |
| |
Hi all,
In update_cpu_capacity(), it will calculate CPU's capacity with RT utilization in mind. Which is introduced in commit e9e9250bc78e7f6342517214c0178a529807964b (https://lkml.org/lkml/2009/8/27/209).
rq->rt_avg and rq->age_stamp are introduced for tracing RT utilization in
a) update_curr_rt sched_rt_avg_update sched_avg_update
b) scheduler_tick cpu_load_update_active cpu_load_update_periodic (or cpu_load_update_nohz) cpu_load_update sched_avg_update
Curious about sched_avg_update(), why "rt->avg / 2^n" (where n denotes periods passed since rq->age_stamp)? - It will be a big summed value if next will meet the end of current period, assuming several RT tasks are running - But it will suddenly reduce to 1/2^n if just passed several periods
So, what is the math behind sched_avg_update()?
-- Regards,
- cee1
| |