Messages in this thread | | | Subject | Re: [RFC PATCH v4 4/6] sched/cpufreq: Introduce sugov_cpu_ramp_boost | From | Douglas Raillard <> | Date | Thu, 23 Jan 2020 17:21:05 +0000 |
| |
On 1/23/20 3:55 PM, Rafael J. Wysocki wrote: > On Wed, Jan 22, 2020 at 6:36 PM Douglas RAILLARD > <douglas.raillard@arm.com> wrote: >> >> Use the utilization signals dynamic to detect when the utilization of a >> set of tasks starts increasing because of a change in tasks' behavior. >> This allows detecting when spending extra power for faster frequency >> ramp up response would be beneficial to the reactivity of the system. >> >> This ramp boost is computed as the difference between util_avg and >> util_est_enqueued. This number somehow represents a lower bound of how >> much extra utilization this tasks is actually using, compared to our >> best current stable knowledge of it (which is util_est_enqueued). >> >> When the set of runnable tasks changes, the boost is disabled as the >> impact of blocked utilization on util_avg will make the delta with >> util_est_enqueued not very informative. >> >> Signed-off-by: Douglas RAILLARD <douglas.raillard@arm.com> >> --- >> kernel/sched/cpufreq_schedutil.c | 43 ++++++++++++++++++++++++++++++++ >> 1 file changed, 43 insertions(+) >> >> diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c >> index 608963da4916..25a410a1ff6a 100644 >> --- a/kernel/sched/cpufreq_schedutil.c >> +++ b/kernel/sched/cpufreq_schedutil.c >> @@ -61,6 +61,10 @@ struct sugov_cpu { >> unsigned long bw_dl; >> unsigned long max; >> >> + unsigned long ramp_boost; >> + unsigned long util_est_enqueued; >> + unsigned long util_avg; >> + >> /* The field below is for single-CPU policies only: */ >> #ifdef CONFIG_NO_HZ_COMMON >> unsigned long saved_idle_calls; >> @@ -183,6 +187,42 @@ static void sugov_deferred_update(struct sugov_policy *sg_policy, u64 time, >> } >> } >> >> +static unsigned long sugov_cpu_ramp_boost(struct sugov_cpu *sg_cpu) >> +{ >> + return READ_ONCE(sg_cpu->ramp_boost); >> +} > > Where exactly is this function used?
In the next commit where the boost value is actually used to do something. The function is introduced here to keep the WRITE_ONCE/READ_ONCE pair together.
> >> + >> +static unsigned long sugov_cpu_ramp_boost_update(struct sugov_cpu *sg_cpu) >> +{ >> + struct rq *rq = cpu_rq(sg_cpu->cpu); >> + unsigned long util_est_enqueued; >> + unsigned long util_avg; >> + unsigned long boost = 0; >> + >> + util_est_enqueued = READ_ONCE(rq->cfs.avg.util_est.enqueued); >> + util_avg = READ_ONCE(rq->cfs.avg.util_avg); >> + >> + /* >> + * Boost when util_avg becomes higher than the previous stable >> + * knowledge of the enqueued tasks' set util, which is CPU's >> + * util_est_enqueued. >> + * >> + * We try to spot changes in the workload itself, so we want to >> + * avoid the noise of tasks being enqueued/dequeued. To do that, >> + * we only trigger boosting when the "amount of work" enqueued >> + * is stable. >> + */ >> + if (util_est_enqueued == sg_cpu->util_est_enqueued && >> + util_avg >= sg_cpu->util_avg && >> + util_avg > util_est_enqueued) >> + boost = util_avg - util_est_enqueued; >> + >> + sg_cpu->util_est_enqueued = util_est_enqueued; >> + sg_cpu->util_avg = util_avg; >> + WRITE_ONCE(sg_cpu->ramp_boost, boost); >> + return boost; >> +} >> + >> /** >> * get_next_freq - Compute a new frequency for a given cpufreq policy. >> * @sg_policy: schedutil policy object to compute the new frequency for. >> @@ -514,6 +554,7 @@ static void sugov_update_single(struct update_util_data *hook, u64 time, >> busy = !sg_policy->need_freq_update && sugov_cpu_is_busy(sg_cpu); >> >> util = sugov_get_util(sg_cpu); >> + sugov_cpu_ramp_boost_update(sg_cpu); >> max = sg_cpu->max; >> util = sugov_iowait_apply(sg_cpu, time, util, max); >> next_f = get_next_freq(sg_policy, util, max); >> @@ -554,6 +595,8 @@ static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu, u64 time) >> unsigned long j_util, j_max; >> >> j_util = sugov_get_util(j_sg_cpu); >> + if (j_sg_cpu == sg_cpu) >> + sugov_cpu_ramp_boost_update(sg_cpu); >> j_max = j_sg_cpu->max; >> j_util = sugov_iowait_apply(j_sg_cpu, time, j_util, j_max); >> >> --
| |