On 22-Jan 11:37, Rafael J. Wysocki wrote: > On Tuesday, January 15, 2019 11:15:05 AM CET Patrick Bellasi wrote: > > Each time a frequency update is required via schedutil, a frequency is > > selected to (possibly) satisfy the utilization reported by each > > scheduling class. However, when utilization clamping is in use, the > > frequency selection should consider userspace utilization clamping > > hints. This will allow, for example, to: > > > > - boost tasks which are directly affecting the user experience > > by running them at least at a minimum "requested" frequency > > > > - cap low priority tasks not directly affecting the user experience > > by running them only up to a maximum "allowed" frequency > > > > These constraints are meant to support a per-task based tuning of the > > frequency selection thus supporting a fine grained definition of > > performance boosting vs energy saving strategies in kernel space. > > > > Add support to clamp the utilization and IOWait boost of RUNNABLE FAIR > > tasks within the boundaries defined by their aggregated utilization > > clamp constraints. > > Based on the max(min_util, max_util) of each task, max-aggregated the > > CPU clamp value in a way to give the boosted tasks the performance they > > need when they happen to be co-scheduled with other capped tasks. > > > > Signed-off-by: Patrick Bellasi <[email protected]> > > Cc: Ingo Molnar <[email protected]> > > Cc: Peter Zijlstra <[email protected]> > > Cc: Rafael J. Wysocki <[email protected]> > > > > --- > > Changes in v6: > > Message-ID: <20181107113849.GC14309@e110439-lin> > > - sanity check util_max >= util_min > > Others: > > - wholesale s/group/bucket/ > > - wholesale s/_{get,put}/_{inc,dec}/ to match refcount APIs > > --- > > kernel/sched/cpufreq_schedutil.c | 27 ++++++++++++++++++++++++--- > > kernel/sched/sched.h | 23 +++++++++++++++++++++++ > > 2 files changed, 47 insertions(+), 3 deletions(-) > > > > diff --git a/kernel/sched/cpufreq_schedutil.c > > b/kernel/sched/cpufreq_schedutil.c > > index 033ec7c45f13..520ee2b785e7 100644 > > --- a/kernel/sched/cpufreq_schedutil.c > > +++ b/kernel/sched/cpufreq_schedutil.c > > @@ -218,8 +218,15 @@ unsigned long schedutil_freq_util(int cpu, unsigned > > long util_cfs, > > * CFS tasks and we use the same metric to track the effective > > * utilization (PELT windows are synchronized) we can directly add them > > * to obtain the CPU's actual utilization. > > + * > > + * CFS utilization can be boosted or capped, depending on utilization > > + * clamp constraints requested by currently RUNNABLE tasks. > > + * When there are no CFS RUNNABLE tasks, clamps are released and > > + * frequency will be gracefully reduced with the utilization decay. > > */ > > - util = util_cfs; > > + util = (type == ENERGY_UTIL) > > + ? util_cfs > > + : uclamp_util(rq, util_cfs); > > util += cpu_util_rt(rq); > > > > dl_util = cpu_util_dl(rq); > > @@ -327,6 +334,7 @@ static void sugov_iowait_boost(struct sugov_cpu > > *sg_cpu, u64 time, > > unsigned int flags) > > { > > bool set_iowait_boost = flags & SCHED_CPUFREQ_IOWAIT; > > + unsigned int max_boost; > > > > /* Reset boost if the CPU appears to have been idle enough */ > > if (sg_cpu->iowait_boost && > > @@ -342,11 +350,24 @@ static void sugov_iowait_boost(struct sugov_cpu > > *sg_cpu, u64 time, > > return; > > sg_cpu->iowait_boost_pending = true; > > > > + /* > > + * Boost FAIR tasks only up to the CPU clamped utilization. > > + * > > + * Since DL tasks have a much more advanced bandwidth control, it's > > + * safe to assume that IO boost does not apply to those tasks. > > + * Instead, since RT tasks are not utilization clamped, we don't want > > + * to apply clamping on IO boost while there is blocked RT > > + * utilization. > > + */ > > + max_boost = sg_cpu->iowait_boost_max; > > + if (!cpu_util_rt(cpu_rq(sg_cpu->cpu))) > > + max_boost = uclamp_util(cpu_rq(sg_cpu->cpu), max_boost); > > + > > /* Double the boost at each request */ > > if (sg_cpu->iowait_boost) { > > sg_cpu->iowait_boost <<= 1; > > - if (sg_cpu->iowait_boost > sg_cpu->iowait_boost_max) > > - sg_cpu->iowait_boost = sg_cpu->iowait_boost_max; > > + if (sg_cpu->iowait_boost > max_boost) > > + sg_cpu->iowait_boost = max_boost; > > return; > > } > > > > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h > > index b7f3ee8ba164..95d62a2a0b44 100644 > > --- a/kernel/sched/sched.h > > +++ b/kernel/sched/sched.h > > @@ -2267,6 +2267,29 @@ static inline unsigned int uclamp_none(int clamp_id) > > return SCHED_CAPACITY_SCALE; > > } > > > > +#ifdef CONFIG_UCLAMP_TASK > > +static inline unsigned int uclamp_util(struct rq *rq, unsigned int util) > > +{ > > + unsigned int min_util = READ_ONCE(rq->uclamp[UCLAMP_MIN].value); > > + unsigned int max_util = READ_ONCE(rq->uclamp[UCLAMP_MAX].value); > > + > > + /* > > + * Since CPU's {min,max}_util clamps are MAX aggregated considering > > + * RUNNABLE tasks with _different_ clamps, we can end up with an > > + * invertion, which we can fix at usage time. > > + */ > > + if (unlikely(min_util >= max_util)) > > + return min_util; > > + > > + return clamp(util, min_util, max_util); > > +} > > +#else /* CONFIG_UCLAMP_TASK */ > > +static inline unsigned int uclamp_util(struct rq *rq, unsigned int util) > > +{ > > + return util; > > +} > > +#endif /* CONFIG_UCLAMP_TASK */ > > + > > #ifdef arch_scale_freq_capacity > > # ifndef arch_scale_freq_invariant > > # define arch_scale_freq_invariant() true > > > > IMO it would be better to combine this patch with the next one.
Main reason was to better document in the changelog what we do for the two different classes... > At least some things in it I was about to ask about would go away > then. :-) ... but if it creates confusion I can certainly merge them. Or maybe clarify better in this patch what's not clear: may I ask what were your questions ? > Besides, I don't really see a reason for the split here. Was mainly to make the changes required for RT more self-contained. For that class only, not for FAIR, we have additional code in the following patch which add uclamp_default_perf which are system defaults used to track/account tasks requesting the maximum frequency. Again, I can either better clarify the above patch or just merge the two together: what do you prefer ? -- #include <best/regards.h> Patrick Bellasi
