Messages in this thread | | | Date | Wed, 18 Oct 2023 12:06:24 +0100 | Subject | Re: [PATCH v2 2/6] topology: add a new arch_scale_freq_reference | From | Lukasz Luba <> |
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On 10/9/23 11:36, Vincent Guittot wrote: > Create a new method to get a unique and fixed max frequency. Currently > cpuinfo.max_freq or the highest (or last) state of performance domain are > used as the max frequency when computing the frequency for a level of > utilization but: > - cpuinfo_max_freq can change at runtime. boost is one example of > such change. > - cpuinfo.max_freq and last item of the PD can be different leading to > different results between cpufreq and energy model. > > We need to save the reference frequency that has been used when computing > the CPUs capacity and use this fixed and coherent value to convert between > frequency and CPU's capacity. > > In fact, we already save the frequency that has been used when computing > the capacity of each CPU. We extend the precision to save khZ instead of > Mhz currently and we modify the type to be aligned with other variables > used when converting frequency to capacity and the other way. > > Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> > --- > 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 | 29 ++++++++++++++--------------- > include/linux/arch_topology.h | 7 +++++++ > 5 files changed, 24 insertions(+), 15 deletions(-)
[snip]
> @@ -170,9 +172,9 @@ DEFINE_PER_CPU(unsigned long, thermal_pressure); > * operating on stale data when hot-plug is used for some CPUs. The > * @capped_freq reflects the currently allowed max CPUs frequency due to > * thermal capping. It might be also a boost frequency value, which is bigger > - * than the internal 'freq_factor' max frequency. In such case the pressure > - * value should simply be removed, since this is an indication that there is > - * no thermal throttling. The @capped_freq must be provided in kHz. > + * than the internal 'capacity_ref_freq' max frequency. In such case the > + * pressure value should simply be removed, since this is an indication that > + * there is no thermal throttling. The @capped_freq must be provided in kHz. > */ > void topology_update_thermal_pressure(const struct cpumask *cpus, > unsigned long capped_freq) > @@ -183,10 +185,7 @@ void topology_update_thermal_pressure(const struct cpumask *cpus, > > cpu = cpumask_first(cpus); > max_capacity = arch_scale_cpu_capacity(cpu); > - max_freq = per_cpu(freq_factor, cpu); > - > - /* Convert to MHz scale which is used in 'freq_factor' */ > - capped_freq /= 1000;
I do like this small speed-up and I'm happy that it's possible with this new design. (IIRC some of your platforms can update the thermal pressure quite many time per sec - that might be the reason why you see some speed-ups mentioned in the cover letter)
> + max_freq = arch_scale_freq_ref(cpu); >
LGTM
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
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