This series demonstrates cpu frequency scaling via a simple policy driven by the scheduler. Specifically the policy evaluates cpu frequency when cpu utilization is updated from enqueue_task_fair and dequeue_task_fair. The policy itself uses a simple up/down threshold scheme using the same 80%/20% cpu utilization boundaries that are used by default in the ondemand cpufreq governor.
This series is not intended for merging, but instead to ignite some discussion around scheduler-driven cpu frequency selection. Of particular interest to me is the policy itself and how it might integrate with task placement in CFS's load_balance. Additionally I'd like to ask the scheduler experts about which call sites in CFS are right for evaluating cpu frequency selection; maybe {en,de}queue_task_fair are not such a good idea?
The messiest part of this series is the cpumask stuff, where I tried to track which cpus have updated statistics in the case of a sched_entity which contains several other sched_entities that are spread across cpus. As discussed at Linux Plumbers Conference 2014, I will replace this complexity with simpler logic that ignores scheduler cgroups in the next version. In any case I am posting the code I have now.
This code is experiemental and bugs are Guaranteed.
These patches are based on the scale invariance series from Morten[0]. The variables names in this RFC will doubtless change once that work is rebased onto Vincent's series[1].
[0] http://lkml.kernel.org/r/1411403047-32010-1-git-send-email-morten.rasmussen@arm.com [1] http://lkml.kernel.org/r/1412684017-16595-1-git-send-email-vincent.guittot@linaro.org
Mike Turquette (6): sched: cfs: declare capacity_of in sched.h sched: fair: add usage_util_of helper cpufreq: add per-governor private data sched: cfs: cpu frequency scaling arch functions sched: cfs: cpu frequency scaling based on task placement sched: energy_model: simple cpu frequency scaling policy
Morten Rasmussen (1): sched: Make energy awareness a sched feature
drivers/cpufreq/Kconfig | 21 +++ include/linux/cpufreq.h | 6 + kernel/sched/Makefile | 1 + kernel/sched/energy_model.c | 341 ++++++++++++++++++++++++++++++++++++++++++++ kernel/sched/fair.c | 69 ++++++++- kernel/sched/features.h | 6 + kernel/sched/sched.h | 3 + 7 files changed, 445 insertions(+), 2 deletions(-) create mode 100644 kernel/sched/energy_model.c