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Date: Mon, 21 Jan 2019 11:15:08 +0100 From: Peter Zijlstra <peterz@...radead.org> To: Patrick Bellasi <patrick.bellasi@....com> Cc: linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org, linux-api@...r.kernel.org, Ingo Molnar <mingo@...hat.com>, Tejun Heo <tj@...nel.org>, "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>, Vincent Guittot <vincent.guittot@...aro.org>, Viresh Kumar <viresh.kumar@...aro.org>, Paul Turner <pjt@...gle.com>, Quentin Perret <quentin.perret@....com>, Dietmar Eggemann <dietmar.eggemann@....com>, Morten Rasmussen <morten.rasmussen@....com>, Juri Lelli <juri.lelli@...hat.com>, Todd Kjos <tkjos@...gle.com>, Joel Fernandes <joelaf@...gle.com>, Steve Muckle <smuckle@...gle.com>, Suren Baghdasaryan <surenb@...gle.com> Subject: Re: [PATCH v6 03/16] sched/core: uclamp: Map TASK's clamp values into CPU's clamp buckets On Tue, Jan 15, 2019 at 10:15:00AM +0000, Patrick Bellasi wrote: > +/* > + * Number of utilization clamp buckets. > + * > + * The first clamp bucket (bucket_id=0) is used to track non clamped tasks, i.e. > + * util_{min,max} (0,SCHED_CAPACITY_SCALE). Thus we allocate one more bucket in > + * addition to the compile time configured number. > + */ > +#define UCLAMP_BUCKETS (CONFIG_UCLAMP_BUCKETS_COUNT + 1) > + > +/* > + * Utilization clamp bucket > + * @value: clamp value tracked by a clamp bucket > + * @bucket_id: the bucket index used by the fast-path > + * @mapped: the bucket index is valid > + * > + * A utilization clamp bucket maps a: > + * clamp value (value), i.e. > + * util_{min,max} value requested from userspace > + * to a: > + * clamp bucket index (bucket_id), i.e. > + * index of the per-cpu RUNNABLE tasks refcounting array > + * > + * The mapped bit is set whenever a task has been mapped on a clamp bucket for > + * the first time. When this bit is set, any: > + * uclamp_bucket_inc() - for a new clamp value > + * is matched by a: > + * uclamp_bucket_dec() - for the old clamp value > + */ > +struct uclamp_se { > + unsigned int value : bits_per(SCHED_CAPACITY_SCALE); > + unsigned int bucket_id : bits_per(UCLAMP_BUCKETS); > + unsigned int mapped : 1; > +}; Do we want something like: BUILD_BUG_ON(sizeof(struct uclamp_se) == sizeof(unsigned int)); And/or put a limit on CONFIG_UCLAMP_BUCKETS_COUNT that guarantees that ?
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