From: Patrick Bellasi <patrick.bellasi@arm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
Ingo Molnar <mingo@redhat.com>, Tejun Heo <tj@kernel.org>,
"Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Viresh Kumar <viresh.kumar@linaro.org>,
Paul Turner <pjt@google.com>,
Quentin Perret <quentin.perret@arm.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Morten Rasmussen <morten.rasmussen@arm.com>,
Juri Lelli <juri.lelli@redhat.com>, Todd Kjos <tkjos@google.com>,
Joel Fernandes <joelaf@google.com>,
Steve Muckle <smuckle@google.com>,
Suren Baghdasaryan <surenb@google.com>
Subject: Re: [PATCH v5 03/15] sched/core: uclamp: map TASK's clamp values into CPU's clamp groups
Date: Wed, 7 Nov 2018 14:24:28 +0000 [thread overview]
Message-ID: <20181107142428.GG14309@e110439-lin> (raw)
In-Reply-To: <20181107134414.GR9781@hirez.programming.kicks-ass.net>
On 07-Nov 14:44, Peter Zijlstra wrote:
> On Mon, Oct 29, 2018 at 06:32:57PM +0000, Patrick Bellasi wrote:
> > +/**
> > + * uclamp_group_get: increase the reference count for a clamp group
> > + * @uc_se: the utilization clamp data for the task
> > + * @clamp_id: the clamp index affected by the task
> > + * @clamp_value: the new clamp value for the task
> > + *
> > + * Each time a task changes its utilization clamp value, for a specified clamp
> > + * index, we need to find an available clamp group which can be used to track
> > + * this new clamp value. The corresponding clamp group index will be used to
> > + * reference count the corresponding clamp value while the task is enqueued on
> > + * a CPU.
> > + */
> > +static void uclamp_group_get(struct uclamp_se *uc_se, unsigned int clamp_id,
> > + unsigned int clamp_value)
> > +{
> > + union uclamp_map *uc_maps = &uclamp_maps[clamp_id][0];
> > + unsigned int prev_group_id = uc_se->group_id;
> > + union uclamp_map uc_map_old, uc_map_new;
> > + unsigned int free_group_id;
> > + unsigned int group_id;
> > + unsigned long res;
> > +
> > +retry:
> > +
> > + free_group_id = UCLAMP_GROUPS;
> > + for (group_id = 0; group_id < UCLAMP_GROUPS; ++group_id) {
> > + uc_map_old.data = atomic_long_read(&uc_maps[group_id].adata);
> > + if (free_group_id == UCLAMP_GROUPS && !uc_map_old.se_count)
> > + free_group_id = group_id;
> > + if (uc_map_old.value == clamp_value)
> > + break;
> > + }
> > + if (group_id >= UCLAMP_GROUPS) {
> > +#ifdef CONFIG_SCHED_DEBUG
> > +#define UCLAMP_MAPERR "clamp value [%u] mapping to clamp group failed\n"
> > + if (unlikely(free_group_id == UCLAMP_GROUPS)) {
> > + pr_err_ratelimited(UCLAMP_MAPERR, clamp_value);
> > + return;
> > + }
> > +#endif
>
> Can you please put in a comment, either here or on top, on why this can
> not in fact happen? And we're always guaranteed a free group.
You right, that's confusing especially because up to this point we are
not granted. We are always granted a free group once we add:
sched/core: uclamp: add clamp group bucketing support
I've kept it separated to better document how we introduce that
support.
Is it ok for for you if I better call out in the change log that the
guarantee comes from a following patch... and add the comment in
that later patch ?
>
> > + group_id = free_group_id;
> > + uc_map_old.data = atomic_long_read(&uc_maps[group_id].adata);
> > + }
> > +
> > + uc_map_new.se_count = uc_map_old.se_count + 1;
> > + uc_map_new.value = clamp_value;
> > + res = atomic_long_cmpxchg(&uc_maps[group_id].adata,
> > + uc_map_old.data, uc_map_new.data);
> > + if (res != uc_map_old.data)
> > + goto retry;
> > +
> > + /* Update SE's clamp values and attach it to new clamp group */
> > + uc_se->value = clamp_value;
> > + uc_se->group_id = group_id;
> > +
> > + /* Release the previous clamp group */
> > + if (uc_se->mapped)
> > + uclamp_group_put(clamp_id, prev_group_id);
> > + uc_se->mapped = true;
> > +}
--
#include <best/regards.h>
Patrick Bellasi
next prev parent reply other threads:[~2018-11-07 14:24 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-29 18:32 [PATCH v5 00/15] Add utilization clamping support Patrick Bellasi
2018-10-29 18:32 ` [PATCH v5 01/15] sched/core: uclamp: extend sched_setattr to support utilization clamping Patrick Bellasi
2018-10-29 19:33 ` Randy Dunlap
2018-11-07 12:09 ` Peter Zijlstra
2018-10-29 18:32 ` [PATCH v5 02/15] sched/core: make sched_setattr able to tune the current policy Patrick Bellasi
2018-11-07 12:11 ` Peter Zijlstra
2018-11-07 13:50 ` Patrick Bellasi
2018-11-07 13:58 ` Peter Zijlstra
2018-10-29 18:32 ` [PATCH v5 03/15] sched/core: uclamp: map TASK's clamp values into CPU's clamp groups Patrick Bellasi
2018-11-07 12:19 ` Peter Zijlstra
2018-11-07 14:19 ` Patrick Bellasi
2018-11-07 14:42 ` Peter Zijlstra
2018-11-07 14:56 ` Patrick Bellasi
2018-11-07 13:16 ` Peter Zijlstra
2018-11-07 13:57 ` Patrick Bellasi
2018-11-07 14:14 ` Peter Zijlstra
2018-11-07 13:35 ` Peter Zijlstra
2018-11-07 14:48 ` Patrick Bellasi
2018-11-07 14:55 ` Peter Zijlstra
2018-11-07 15:04 ` Patrick Bellasi
2018-11-07 13:44 ` Peter Zijlstra
2018-11-07 14:24 ` Patrick Bellasi [this message]
2018-11-07 14:44 ` Peter Zijlstra
2018-11-07 14:58 ` Patrick Bellasi
2018-11-07 14:37 ` Peter Zijlstra
2018-11-07 14:53 ` Patrick Bellasi
2018-10-29 18:32 ` [PATCH v5 04/15] sched/core: uclamp: add CPU's clamp groups accounting Patrick Bellasi
2018-10-29 18:42 ` Patrick Bellasi
2018-10-29 18:32 ` [PATCH v5 04/15] sched/core: uclamp: add CPU's clamp groups refcounting Patrick Bellasi
2018-11-11 16:47 ` Peter Zijlstra
2018-11-13 15:11 ` Patrick Bellasi
2018-11-22 14:20 ` Patrick Bellasi
2018-10-29 18:33 ` [PATCH v5 05/15] sched/core: uclamp: update CPU's refcount on clamp changes Patrick Bellasi
2018-10-29 18:33 ` [PATCH v5 06/15] sched/core: uclamp: enforce last task UCLAMP_MAX Patrick Bellasi
2018-11-11 17:08 ` Peter Zijlstra
2018-11-13 15:14 ` Patrick Bellasi
2018-10-29 18:33 ` [PATCH v5 07/15] sched/core: uclamp: add clamp group bucketing support Patrick Bellasi
2018-11-12 0:09 ` Peter Zijlstra
2018-11-13 15:29 ` Patrick Bellasi
2018-10-29 18:33 ` [PATCH v5 08/15] sched/core: uclamp: add system default clamps Patrick Bellasi
2018-10-29 18:33 ` [PATCH v5 09/15] sched/cpufreq: uclamp: add utilization clamping for FAIR tasks Patrick Bellasi
2018-11-07 11:38 ` Patrick Bellasi
2018-10-29 18:33 ` [PATCH v5 10/15] sched/cpufreq: uclamp: add utilization clamping for RT tasks Patrick Bellasi
2018-10-29 18:33 ` [PATCH v5 11/15] sched/core: uclamp: extend CPU's cgroup controller Patrick Bellasi
2018-10-29 18:33 ` [PATCH v5 12/15] sched/core: uclamp: propagate parent clamps Patrick Bellasi
2018-10-29 18:33 ` [PATCH v5 13/15] sched/core: uclamp: map TG's clamp values into CPU's clamp groups Patrick Bellasi
2018-10-29 18:33 ` [PATCH v5 14/15] sched/core: uclamp: use TG's clamps to restrict Task's clamps Patrick Bellasi
2018-10-29 18:47 ` Patrick Bellasi
2018-10-29 18:33 ` [PATCH v5 14/15] sched/core: uclamp: use TG's clamps to restrict TASK's clamps Patrick Bellasi
2018-10-29 18:33 ` [PATCH v5 15/15] sched/core: uclamp: update CPU's refcount on TG's clamp changes Patrick Bellasi
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