[PATCH 0/4] consolidate and cleanup CPU capacity
Vincent Guittot
vincent.guittot at linaro.org
Mon Sep 25 05:05:43 PDT 2023
On Thu, 21 Sept 2023 at 12:12, Ionela Voinescu <ionela.voinescu at arm.com> wrote:
>
> On Friday 01 Sep 2023 at 15:03:08 (+0200), Vincent Guittot wrote:
> > This is the 1st part of consolidating how the max compute capacity is
> > used in the scheduler and how we calculate the frequency for a level of
> > utilization.
> >
> > Fix some unconsistancy when computing frequency for an utilization. There
> > can be a mismatch between energy model and schedutil.
>
> There are a few more pieces of functionality that would be worth
> consolidating in this set as well, if you'd like to consider them:
>
> - arch_set_freq_scale() still uses policy->cpuinfo.max_freq. It might be
> good to use the boot time stored max_freq here as well. Given that
> arch_scale_cpu_capacity() would be based on that stored value, if
> arch_scale_freq_capacity() ends up using a different value, it could
> have interesting effects on the utilization signals in case of
> boosting.
That's a good point, I will have a look at this part too. From a quick
look, this seems to be only used by architecture that are using
arch_topology.c too
>
> - As Pierre mentioned in a previous comment, there is already a
> cpufreq_get_hw_max_freq() weak function that returns
> policy->cpuinfo.max_freq and it's only used at boot time by
> the setup code for AMU use for frequency invariance. I'm tempted to
> suggest to use this to initialize what is now "freq_factor" as my
> intention when I created that function was to provide platform
> providers with the possibility to implement their own and decide on
> the frequency they choose as their maximum. This could have been an
> arch_ function as well, but as you mentioned before, mobile and server
> platforms might want to choose different maximum values even if they
> are using the same architecture.
>
> Thanks,
> Ionela.
>
> >
> > Next step will be to make a difference between the original
> > max compute capacity of a CPU and what is currently available when
> > there is a capping applying forever (i.e. seconds or more).
> >
> > Vincent Guittot (4):
> > sched: consolidate and cleanup access to CPU's max compute capacity
> > topology: add a new arch_scale_freq_reference
> > cpufreq/schedutil: use a fixed reference frequency
> > energy_model: use a fixed reference frequency
> >
> > arch/arm/include/asm/topology.h | 1 +
> > arch/arm64/include/asm/topology.h | 1 +
> > arch/riscv/include/asm/topology.h | 1 +
> > drivers/base/arch_topology.c | 9 +++------
> > include/linux/arch_topology.h | 7 +++++++
> > include/linux/energy_model.h | 20 +++++++++++++++++---
> > kernel/sched/core.c | 2 +-
> > kernel/sched/cpudeadline.c | 2 +-
> > kernel/sched/cpufreq_schedutil.c | 29 +++++++++++++++++++++++++++--
> > kernel/sched/deadline.c | 4 ++--
> > kernel/sched/fair.c | 18 ++++++++----------
> > kernel/sched/rt.c | 2 +-
> > kernel/sched/sched.h | 6 ------
> > kernel/sched/topology.c | 7 +++++--
> > 14 files changed, 75 insertions(+), 34 deletions(-)
> >
> > --
> > 2.34.1
> >
> >
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