From mboxrd@z Thu Jan 1 00:00:00 1970 From: Patrick Bellasi Subject: [PATCH v7 14/15] sched/core: uclamp: Use TG's clamps to restrict TASK's clamps Date: Fri, 8 Feb 2019 10:05:53 +0000 Message-ID: <20190208100554.32196-15-patrick.bellasi@arm.com> References: <20190208100554.32196-1-patrick.bellasi@arm.com> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20190208100554.32196-1-patrick.bellasi@arm.com> Sender: linux-kernel-owner@vger.kernel.org To: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, linux-api@vger.kernel.org Cc: Ingo Molnar , Peter Zijlstra , Tejun Heo , "Rafael J . Wysocki" , Vincent Guittot , Viresh Kumar , Paul Turner , Quentin Perret , Dietmar Eggemann , Morten Rasmussen , Juri Lelli , Todd Kjos , Joel Fernandes , Steve Muckle , Suren Baghdasaryan List-Id: linux-api@vger.kernel.org When a task specific clamp value is configured via sched_setattr(2), this value is accounted in the corresponding clamp bucket every time the task is {en,de}qeued. However, when cgroups are also in use, the task specific clamp values could be restricted by the task_group (TG) clamp values. Update uclamp_cpu_inc() to aggregate task and TG clamp values. Every time a task is enqueued, it's accounted in the clamp_bucket defining the smaller clamp between the task specific value and its TG effective value. This allows to: 1. ensure cgroup clamps are always used to restrict task specific requests, i.e. boosted only up to the effective granted value or clamped at least to a certain value 2. implement a "nice-like" policy, where tasks are still allowed to request less then what enforced by their current TG This mimics what already happens for a task's CPU affinity mask when the task is also in a cpuset, i.e. cgroup attributes are always used to restrict per-task attributes. Do this by exploiting the concept of "effective" clamp, which is already used by a TG to track parent enforced restrictions. Apply task group clamp restrictions only to tasks belonging to a child group. While, for tasks in the root group or in an autogroup, only system defaults are enforced. Signed-off-by: Patrick Bellasi Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Tejun Heo --- kernel/sched/core.c | 42 +++++++++++++++++++++++++++++++++++++++++- 1 file changed, 41 insertions(+), 1 deletion(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 35e9f06af08d..6f8f68d18d0f 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -823,10 +823,44 @@ static inline void uclamp_rq_update(struct rq *rq, unsigned int clamp_id, WRITE_ONCE(rq->uclamp[clamp_id].value, max_value); } +static inline bool +uclamp_tg_restricted(struct task_struct *p, unsigned int clamp_id, + unsigned int *clamp_value, unsigned int *bucket_id) +{ +#ifdef CONFIG_UCLAMP_TASK_GROUP + unsigned int clamp_max, bucket_max; + struct uclamp_se *tg_clamp; + + /* + * Tasks in an autogroup or the root task group are restricted by + * system defaults. + */ + if (task_group_is_autogroup(task_group(p))) + return false; + if (task_group(p) == &root_task_group) + return false; + + tg_clamp = &task_group(p)->uclamp[clamp_id]; + bucket_max = tg_clamp->effective.bucket_id; + clamp_max = tg_clamp->effective.value; + + if (!p->uclamp[clamp_id].user_defined || *clamp_value > clamp_max) { + *clamp_value = clamp_max; + *bucket_id = bucket_max; + } + + return true; +#else + return false; +#endif +} + /* * The effective clamp bucket index of a task depends on, by increasing * priority: * - the task specific clamp value, when explicitly requested from userspace + * - the task group effective clamp value, for tasks not either in the root + * group or in an autogroup * - the system default clamp value, defined by the sysadmin * * As a side effect, update the task's effective value: @@ -841,7 +875,13 @@ uclamp_effective_get(struct task_struct *p, unsigned int clamp_id, *bucket_id = p->uclamp[clamp_id].bucket_id; *clamp_value = p->uclamp[clamp_id].value; - /* Always apply system default restrictions */ + /* + * If we have task groups and we are running in a child group, system + * default are already affecting the group's clamp values. + */ + if (uclamp_tg_restricted(p, clamp_id, clamp_value, bucket_id)) + return; + if (unlikely(*clamp_value > uclamp_default[clamp_id].value)) { *clamp_value = uclamp_default[clamp_id].value; *bucket_id = uclamp_default[clamp_id].bucket_id; -- 2.20.1