Messages in this thread | | | From | Suren Baghdasaryan <> | Date | Sat, 21 Jul 2018 20:17:57 -0700 | Subject | Re: [PATCH v2 11/12] sched/core: uclamp: update CPU's refcount on TG's clamp changes |
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On Mon, Jul 16, 2018 at 1:29 AM, Patrick Bellasi <patrick.bellasi@arm.com> wrote: > When a task group refcounts a new clamp group, we need to ensure that > the new clamp values are immediately enforced to all its tasks which are > currently RUNNABLE. This is to ensure that all currently RUNNABLE task
tasks
> are boosted and/or clamped as requested as soon as possible. > > Let's ensure that, whenever a new clamp group is refcounted by a task > group, all its RUNNABLE tasks are correctly accounted in their > respective CPUs. We do that by slightly refactoring uclamp_group_get() > to get an additional parameter *cgroup_subsys_state which, when > provided, it's used to walk the list of tasks in the correspond TGs and
corresponding TGs
> update the RUNNABLE ones. > > This is a "brute force" solution which allows to reuse the same refcount > update code already used by the per-task API. That's also the only way > to ensure a prompt enforcement of new clamp constraints on RUNNABLE > tasks, as soon as a task group attribute is tweaked. > > Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com> > Cc: Ingo Molnar <mingo@redhat.com> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Tejun Heo <tj@kernel.org> > Cc: Paul Turner <pjt@google.com> > Cc: Todd Kjos <tkjos@google.com> > Cc: Joel Fernandes <joelaf@google.com> > Cc: Steve Muckle <smuckle@google.com> > Cc: Juri Lelli <juri.lelli@redhat.com> > Cc: Dietmar Eggemann <dietmar.eggemann@arm.com> > Cc: Morten Rasmussen <morten.rasmussen@arm.com> > Cc: linux-kernel@vger.kernel.org > Cc: linux-pm@vger.kernel.org > --- > kernel/sched/core.c | 42 ++++++++++++++++++++++++++++++++++-------- > 1 file changed, 34 insertions(+), 8 deletions(-) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 50613d3d5b83..42cff5ffddae 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -1198,21 +1198,43 @@ static inline void uclamp_group_put(int clamp_id, int group_id) > raw_spin_unlock_irqrestore(&uc_map[group_id].se_lock, flags); > } > > +static inline void uclamp_group_get_tg(struct cgroup_subsys_state *css, > + int clamp_id, unsigned int group_id) > +{ > + struct css_task_iter it; > + struct task_struct *p; > + > + /* Update clamp groups for RUNNABLE tasks in this TG */ > + css_task_iter_start(css, 0, &it); > + while ((p = css_task_iter_next(&it))) > + uclamp_task_update_active(p, clamp_id, group_id); > + css_task_iter_end(&it); > +} > + > /** > * uclamp_group_get: increase the reference count for a clamp group > * @p: the task which clamp value must be tracked > - * @clamp_id: the clamp index affected by the task > - * @uc_se: the utilization clamp data for the task > - * @clamp_value: the new clamp value for the task > + * @css: the task group which clamp value must be tracked > + * @clamp_id: the clamp index affected by the task (group) > + * @uc_se: the utilization clamp data for the task (group) > + * @clamp_value: the new clamp value for the task (group) > * > * 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 by > * the task to reference count the clamp value on CPUs while enqueued. > * > + * When the cgroup's cpu controller utilization clamping support is enabled, > + * each task group has a set of clamp values which are used to restrict the > + * corresponding task specific clamp values. > + * When a clamp value for a task group is changed, all the (active) tasks > + * belonging to that task group must be update to ensure they are refcounting
must be updated
> + * the correct CPU's clamp value. > + * > * Return: -ENOSPC if there are no available clamp groups, 0 on success. > */ > static inline int uclamp_group_get(struct task_struct *p, > + struct cgroup_subsys_state *css, > int clamp_id, struct uclamp_se *uc_se, > unsigned int clamp_value) > { > @@ -1240,6 +1262,10 @@ static inline int uclamp_group_get(struct task_struct *p, > uc_map[next_group_id].se_count += 1; > raw_spin_unlock_irqrestore(&uc_map[next_group_id].se_lock, flags); > > + /* Newly created TG don't have tasks assigned */ > + if (css) > + uclamp_group_get_tg(css, clamp_id, next_group_id); > + > /* Update CPU's clamp group refcounts of RUNNABLE task */ > if (p) > uclamp_task_update_active(p, clamp_id, next_group_id); > @@ -1307,7 +1333,7 @@ static inline int alloc_uclamp_sched_group(struct task_group *tg, > uc_se->value = parent->uclamp[clamp_id].value; > uc_se->group_id = UCLAMP_NONE; > > - if (uclamp_group_get(NULL, clamp_id, uc_se, > + if (uclamp_group_get(NULL, NULL, clamp_id, uc_se, > parent->uclamp[clamp_id].value)) { > ret = 0; > goto out; > @@ -1362,12 +1388,12 @@ static inline int __setscheduler_uclamp(struct task_struct *p, > > /* Update min utilization clamp */ > uc_se = &p->uclamp[UCLAMP_MIN]; > - retval |= uclamp_group_get(p, UCLAMP_MIN, uc_se, > + retval |= uclamp_group_get(p, NULL, UCLAMP_MIN, uc_se, > attr->sched_util_min); > > /* Update max utilization clamp */ > uc_se = &p->uclamp[UCLAMP_MAX]; > - retval |= uclamp_group_get(p, UCLAMP_MAX, uc_se, > + retval |= uclamp_group_get(p, NULL, UCLAMP_MAX, uc_se, > attr->sched_util_max); > > mutex_unlock(&uclamp_mutex); > @@ -7274,7 +7300,7 @@ static int cpu_util_min_write_u64(struct cgroup_subsys_state *css, > > /* Update TG's reference count */ > uc_se = &tg->uclamp[UCLAMP_MIN]; > - ret = uclamp_group_get(NULL, UCLAMP_MIN, uc_se, min_value); > + ret = uclamp_group_get(NULL, css, UCLAMP_MIN, uc_se, min_value); > > out: > rcu_read_unlock(); > @@ -7306,7 +7332,7 @@ static int cpu_util_max_write_u64(struct cgroup_subsys_state *css, > > /* Update TG's reference count */ > uc_se = &tg->uclamp[UCLAMP_MAX]; > - ret = uclamp_group_get(NULL, UCLAMP_MAX, uc_se, max_value); > + ret = uclamp_group_get(NULL, css, UCLAMP_MAX, uc_se, max_value); > > out: > rcu_read_unlock(); > -- > 2.17.1 >
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