| Message ID | 20190508174301.4828-1-douglas.raillard@arm.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | sched/cpufreq: Make schedutil energy aware | expand |
On Wed, May 8, 2019 at 11:57 PM <douglas.raillard@arm.com> wrote: > > From: Douglas RAILLARD <douglas.raillard@arm.com> > > Make schedutil cpufreq governor energy-aware. Hi Douglas, I was wondering on why the cpufreq maintainers weren't cc'd for this set and then I noticed that get_maintainers doesn't report us at all for schedutil :( I have sent a patch to fix that, but please include us as well in the future even if get_maintainers doesn't report us :) -- viresh
Hi Viresh, Rafael, On 5/13/19 8:12 AM, Viresh Kumar wrote: > On Wed, May 8, 2019 at 11:57 PM <douglas.raillard@arm.com> wrote: >> >> From: Douglas RAILLARD <douglas.raillard@arm.com> >> >> Make schedutil cpufreq governor energy-aware. > > Hi Douglas, > > I was wondering on why the cpufreq maintainers weren't cc'd for this set and > then I noticed that get_maintainers doesn't report us at all for schedutil :( > > I have sent a patch to fix that, but please include us as well in the > future even > if get_maintainers doesn't report us :) Looks like it was a mix of me not checking my checklist and get_maintainers not catching it, I'll make sure both of you are in CC next time :) > > -- > viresh Thanks, Douglas
From: Douglas RAILLARD <douglas.raillard@arm.com> Make schedutil cpufreq governor energy-aware. - patch 1 introduces a function to retrieve a frequency given a base frequency and an energy cost margin. - patch 2 links Energy Model perf_domain to sugov_policy. - patch 3 updates get_next_freq() to make use of the Energy Model. - patch 4 moves a static function around in cpufreq_schedutil.c to make it available for subsequent patch. - patch 5 updates sugov_cpu_is_busy() to make it useable for shared cpufreq policies. - patch 6 improves sugov_cpu_is_busy() to avoid some pitfalls when used from shared policies. - patch 7 makes use of sugov_cpu_is_busy() for frequency selection of shared cpufreq policies. The benefits of using the EM in schedutil are twofold: 1) Selecting the highest possible frequency for a given cost. Some platforms can have lower frequencies that are less efficient than higher ones, in which case they should be skipped for most purposes. They can still be useful to give more freedom to thermal throttling mechanisms, but not under normal circumstances. note: the EM framework will warn about such OPPs "hertz/watts ratio non-monotonically decreasing" 2) Drive the frequency selection with power in mind, in addition to maximizing the utilization of the non-idle CPUs in the system. Point 1) is implemented in "PM: Introduce em_pd_get_higher_freq()" and enabled in schedutil by "sched/cpufreq: Hook em_pd_get_higher_power() into get_next_freq()". Point 2) is enabled in "sched/cpufreq: Boost schedutil frequency ramp up". It allows using higher frequencies when a CPU is "busy" in the policy, reusing the existing sugov_cpu_is_busy() schedutil heuristic. "busy" is defined here as not having any idle time since the last increase in frequency. The benefits of that are: * Boosting the frequency when it (seems) needed by a CPU to finish its allocated work. That shortens the frequency ramp up duration, which in turns allows the utilization signal to reach stable values quicker. Since the allowed frequency boost is bounded in energy, it will behave consistently across platforms, regardless of the OPP cost range. * The boost is only transient, and should not impact a lot the energy consumed of workloads with very stable utilization signals. This has been ligthly tested with a rtapp task ramping from 10% to 75% utilisation on a big core. Improvements in frequency ramp-up time are somehow diminished by the shape of the utilisation signal, which gives a big oscillation to the signal after a fast ramp up with idle time. It however improves the time it takes to reach the final frequency, but some activations are still missed due to strong frequency decrease right after ramping up. Douglas RAILLARD (7): PM: Introduce em_pd_get_higher_freq() sched/cpufreq: Attach perf domain to sugov policy sched/cpufreq: Hook em_pd_get_higher_power() into get_next_freq() sched/cpufreq: Move up sugov_cpu_is_busy() sched/cpufreq: sugov_cpu_is_busy for shared policy sched/cpufreq: Improve sugov_cpu_is_busy accuracy sched/cpufreq: Boost schedutil frequency ramp up include/linux/energy_model.h | 48 +++++++++++ kernel/sched/cpufreq_schedutil.c | 136 +++++++++++++++++++++++++++---- 2 files changed, 166 insertions(+), 18 deletions(-)