On Tue, Feb 06, 2018 at 06:33:15PM +0000, Patrick Bellasi wrote: > Good point, I was actually expecting this question and I should have > added it to the cover letter, sorry. > > The reasoning was: the task's estimated utilization is defined as the > max between PELT and the "estimation". Where "estimation" is > the max between EWMA and the last ENQUEUED utilization. > > Thus I was envisioning these two calls: > > _task_util_est := max(EWMA, ENQUEUED) > task_util_est := max(util_avg, _task_util_est) > > but since now we have clients only for the first API, I've not added > the second one. Still I would prefer to keep the "_" to make it clear > that's and util_est's internal signal, not the actual task's estimated > utilization. > > Does it make sense? > > Do you prefer I just remove the "_" and we will refactor it once we > should add a customer for the proper task's util_est?
Hurm... I was thinking: task_util_est := max(util_avg, EWMA) But the above mixes ENQUEUED into it.. *confused*. Also, I think I'm confused by the 'enqueued' name... it makes sense for the cfs use-case, where we track the sum of all 'enqueued' tasks, but it doesn't make sense for the task use-case where it tracks task_util() at dequeue time. > > > +/* > > > + * Check if the specified (signed) value is within a specified margin, > > > + * based on the observation that: > > > + * abs(x) < y := (unsigned)(x + y - 1) < (2 * y - 1) > > > + */ > > > +static inline bool within_margin(long value, unsigned int margin) > > > > This mixing of long and int is dodgy, do we want to consistently use int > > here? > > Right, perhaps better "unsigned int" for both params, isn't? Can't, must be signed, since @value is supposed to be able to be negative remember? ;-) > > > + WRITE_ONCE(cfs_rq->avg.util_est.enqueued, util_est); > > > + WRITE_ONCE(p->se.avg.util_est.enqueued, util_last); > > > > Two stores to that word... can we fix that nicely? > > Good point, the single word comes from the goal to fit into the same > cache line of sched_avg. Its the above two stores I confuzzled to be the same. So n/m all that. > > > +SCHED_FEAT(UTIL_EST, false) > > > > Since you couldn't measure it, do we wants it true? > > I'm just a single tester so far, I would be more confident once > someone volunteer to turn this on to give a better coverage. Lets just enable it by default, that way its far more likely someone will complain about it :-), disabling it again is a trivial matter when needed. Also, your patch 2/3 have insufficient READ_ONCE()s.
