Messages in this thread Patch in this message | | | Date | Thu, 21 Sep 2023 10:19:40 +0100 | From | Ionela Voinescu <> | Subject | Re: [PATCH 3/4] cpufreq/schedutil: use a fixed reference frequency |
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On Friday 01 Sep 2023 at 15:03:11 (+0200), Vincent Guittot wrote: > cpuinfo_max_freq can change at runtime because of boost as example. This > implies that the value could not be the same than the one that has been > used when computing the capacity of a CPU. > > The new arch_scale_freq_ref() returns a fixed and coherent frequency > reference that can be used when computing a frequency based on utilization. > > Use this arch_scale_freq_ref() when available and fallback to > cpuinfo.max_freq otherwise. > > Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> > --- > kernel/sched/cpufreq_schedutil.c | 29 +++++++++++++++++++++++++++-- > 1 file changed, 27 insertions(+), 2 deletions(-) > > diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c > index 4492608b7d7f..9996ef429e2b 100644 > --- a/kernel/sched/cpufreq_schedutil.c > +++ b/kernel/sched/cpufreq_schedutil.c > @@ -114,6 +114,31 @@ static void sugov_deferred_update(struct sugov_policy *sg_policy) > } > } > > +#ifdef arch_scale_freq_ref > +/** > + * arch_scale_freq_ref_policy - get the reference frequency of a given CPU that > + * has been used to correlate frequency and compute capacity. > + * @cpu: the CPU in question. > + * > + * Return: the reference CPU frequency. > + */ > +static __always_inline > +unsigned long arch_scale_freq_ref_policy(struct cpufreq_policy *policy)
This should not be an arch_ function as it's only a wrapper over an arch_ function and not a function that different architectures might implement differently usually in architecture specific code.
> +{ > + return arch_scale_freq_ref(policy->cpu);
It might make it easier to read if arch_scale_freq_ref() had a default implementation that returned 0.
Then this code would simply become:
freq = arch_scale_freq_ref(policy->cpu); if (freq) return freq; else if (arch_scale_freq_invariant()) return .. ..
This approach is similar to the use of arch_freq_get_on_cpu() in cpufreq.c, and, as there, having a chosen maximum frequency of 0 would not be a valid value.
> +} > +#else > +static __always_inline > +unsigned long arch_scale_freq_ref_policy(struct cpufreq_policy *policy) > +{ > + if (arch_scale_freq_invariant()) > + return policy->cpuinfo.max_freq; > + > + > + return policy->cur; > +} > +#endif > + > /** > * get_next_freq - Compute a new frequency for a given cpufreq policy. > * @sg_policy: schedutil policy object to compute the new frequency for. > @@ -139,11 +164,11 @@ static void sugov_deferred_update(struct sugov_policy *sg_policy) > static unsigned int get_next_freq(struct sugov_policy *sg_policy, > unsigned long util, unsigned long max) > { > + unsigned int freq; > struct cpufreq_policy *policy = sg_policy->policy; > - unsigned int freq = arch_scale_freq_invariant() ? > - policy->cpuinfo.max_freq : policy->cur; > > util = map_util_perf(util); > + freq = arch_scale_freq_ref_policy(policy);
Given its single use here, it would likely be better to place the code above directly here, rather than create a wrapper over a few lines of code.
Hope it helps, Ionela.
> freq = map_util_freq(util, freq, max); > > if (freq == sg_policy->cached_raw_freq && !sg_policy->need_freq_update) > -- > 2.34.1 > >
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