On Thu, 30 Nov 2023 at 14:42, Dietmar Eggemann <dietmar.eggemann@xxxxxxx> wrote: > > On 27/11/2023 15:32, Vincent Guittot wrote: > > With UTIL_EST_FASTUP now being permanent, we can take advantage of the > > fact that the ewma jumps directly to a higher utilization at dequeue to > > simplify util_est and remove the enqueued field. > > > > Did some simple test with a ramp-up/ramp_down (10-80-10%) task affine to > a CPU. > > https://nbviewer.org/github/deggeman/lisa/blob/ipynbs/ipynb/scratchpad/util_est_fastup.ipynb > > LGTM. Thanks > > [...] > > > @@ -4879,27 +4865,22 @@ static inline void util_est_update(struct cfs_rq *cfs_rq, > > * Skip update of task's estimated utilization when its members are > > * already ~1% close to its last activation value. > > */ > > - last_ewma_diff = ue.enqueued - ue.ewma; > > - last_enqueued_diff -= ue.enqueued; > > - if (within_margin(last_ewma_diff, UTIL_EST_MARGIN)) { > > - if (!within_margin(last_enqueued_diff, UTIL_EST_MARGIN)) > > - goto done; > > - > > - return; > > - } > > + last_ewma_diff = ewma - dequeued; > > + if (last_ewma_diff < UTIL_EST_MARGIN) > > + goto done; > > > > /* > > * To avoid overestimation of actual task utilization, skip updates if > > * we cannot grant there is idle time in this CPU. > > */ > > - if (task_util(p) > arch_scale_cpu_capacity(cpu_of(rq_of(cfs_rq)))) > > + if (dequeued > arch_scale_cpu_capacity(cpu_of(rq_of(cfs_rq)))) > > return; > > Not directly related to the changes: Should we not use `goto done` here > is well to rearm UTIL_AVG_UNCHANGED? I noticed this as well but didn't want to mix 2 topics. > > > /* > > * To avoid underestimate of task utilization, skip updates of EWMA if > > * we cannot grant that thread got all CPU time it wanted. > > */ > > - if ((ue.enqueued + UTIL_EST_MARGIN) < task_runnable(p)) > > + if ((dequeued + UTIL_EST_MARGIN) < task_runnable(p)) > > goto done; > > > > > > @@ -4914,18 +4895,18 @@ static inline void util_est_update(struct cfs_rq *cfs_rq, > > * ewma(t) = w * task_util(p) + (1-w) * ewma(t-1) > > * = w * task_util(p) + ewma(t-1) - w * ewma(t-1) > > * = w * (task_util(p) - ewma(t-1)) + ewma(t-1) > > - * = w * ( last_ewma_diff ) + ewma(t-1) > > - * = w * (last_ewma_diff + ewma(t-1) / w) > > + * = w * ( -last_ewma_diff ) + ewma(t-1) > > + * = w * (-last_ewma_diff + ewma(t-1) / w) > > * > > * Where 'w' is the weight of new samples, which is configured to be > > * 0.25, thus making w=1/4 ( >>= UTIL_EST_WEIGHT_SHIFT) > > */ > > The text above still mentioned ue.enqueued and that we store the current > PELT value ... which isn't the case anymore. argh, I missed this one > > > > - ue.ewma <<= UTIL_EST_WEIGHT_SHIFT; > > - ue.ewma += last_ewma_diff; > > - ue.ewma >>= UTIL_EST_WEIGHT_SHIFT; > > + ewma <<= UTIL_EST_WEIGHT_SHIFT; > > + ewma -= last_ewma_diff; > > + ewma >>= UTIL_EST_WEIGHT_SHIFT; > > done: > > - ue.enqueued |= UTIL_AVG_UNCHANGED; > > - WRITE_ONCE(p->se.avg.util_est, ue); > > + ewma |= UTIL_AVG_UNCHANGED; > > + WRITE_ONCE(p->se.avg.util_est, ewma); > > > > trace_sched_util_est_se_tp(&p->se); > > } > > [...] > > Reviewed-by: Dietmar Eggemann <dietmar.eggemann@xxxxxxx> Thanks
