On Mon, Aug 15, 2016 at 04:23:42PM +0200, Peter Zijlstra wrote: > On Mon, Jul 25, 2016 at 02:34:27PM +0100, Morten Rasmussen wrote: > > To solve this problem, this patch introduces task_util_wake() which > > computes the decayed task utilization based on the last update of the > > previous cpu's last load-tracking update. It is done without having to > > take the rq lock, similar to how it is done in remove_entity_load_avg(). > > But unlike that function, it doesn't actually use __update_load_avg(). > Why not?
Fair question :) We currently exploit the fact that the task utilization is _not_ updated in wake-up balancing to make sure we don't under-estimate the capacity requirements for tasks that have slept for a while. If we update it, we loose the non-decayed 'peak' utilization, but I guess we could just store it somewhere when we do the wake-up decay. I thought there was a better reason when I wrote the patch, but I don't recall right now. I will look into it again and see if we can use __update_load_avg() to do a proper update instead of doing things twice.
