Messages in this thread | | | Date | Thu, 30 Nov 2017 14:28:59 +0100 | From | Juri Lelli <> | Subject | Re: [PATCH v3 4/6] sched/rt: fast switch to maximum frequency when RT tasks are scheduled |
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Hi,
On 30/11/17 11:47, Patrick Bellasi wrote: > Currently schedutil updates are triggered for the RT class using a single > call place, which is part of the rt::update_curr_rt() used in: > > - dequeue_task_rt: > but it does not make sense to set the schedutil's SCHED_CPUFREQ_RT in > case the next task should not be an RT one > > - put_prev_task_rt: > likewise, we set the SCHED_CPUFREQ_RT flag without knowing if required > by the next task > > - pick_next_task_rt: > likewise, the schedutil's SCHED_CPUFREQ_RT is set in case the prev task > was RT, while we don't yet know if the next will be RT > > - task_tick_rt: > that's the only really useful call, which can ramp up the frequency in > case a RT task started its execution without a chance to order a > frequency switch (e.g. because of the schedutil ratelimit) > > Apart from the last call in task_tick_rt, the others are at least useless. > Thus, although being a simple solution, not all the call sites of that > update_curr_rt() are interesting to trigger a frequency switch as well as > some of the most interesting points are not covered by that call. > For example, a task set to RT has to wait the next tick to get the > frequency boost. > > This patch fixes these issues by placing explicitly the schedutils > update calls in the only sensible places, which are: > - when an RT task wakes up and it's enqueued in a CPU > - when we actually pick a RT task for execution > - at each tick time > - when a task is set to be RT > > Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com> > Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Reviewed-by: Juri Lelli <juri.lelli@redhat.com>
Best,
Juri
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