Messages in this thread | | | From | "Rafael J. Wysocki" <> | Date | Tue, 25 Jul 2023 20:31:29 +0200 | Subject | Re: [PATCH] x86/aperfmperf: Make stale CPU frequency response within limits. |
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On Tue, Jul 25, 2023 at 2:14 AM Doug Smythies <dsmythies@telus.net> wrote: > > Currently, when the CPU frequency is stale the nominal clock frequency > is returned by calls to arch_freq_get_on_cpu(). Some users are > confused by the high reported frequency when their system is idle > and/or it is above a reduced maximum they set. > > This patch will return the policy minimum as the stale frequency reply > from arch_freq_get_on_cpu(). > > Reported-by: Yang Jie <yang.jie@linux.intel.com> > Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=217597 > Signed-off-by: Doug Smythies <dsmythies@telus.net> > --- > arch/x86/kernel/cpu/aperfmperf.c | 13 +++++-------- > drivers/cpufreq/cpufreq.c | 18 ++++++++++++++++++ > include/linux/cpufreq.h | 5 +++++ > 3 files changed, 28 insertions(+), 8 deletions(-) > > diff --git a/arch/x86/kernel/cpu/aperfmperf.c b/arch/x86/kernel/cpu/aperfmperf.c > index fdbb5f07448f..44cc96864d94 100644 > --- a/arch/x86/kernel/cpu/aperfmperf.c > +++ b/arch/x86/kernel/cpu/aperfmperf.c > @@ -418,9 +418,10 @@ unsigned int arch_freq_get_on_cpu(int cpu) > unsigned long last; > u64 acnt, mcnt; > > - if (!cpu_feature_enabled(X86_FEATURE_APERFMPERF)) > - goto fallback; > - > + if (!cpu_feature_enabled(X86_FEATURE_APERFMPERF)){ > + freq = cpufreq_quick_get(cpu); > + return freq ? freq : cpufreq_quick_get_min(cpu); > + } > do { > seq = raw_read_seqcount_begin(&s->seq); > last = s->last_update; > @@ -433,13 +434,9 @@ unsigned int arch_freq_get_on_cpu(int cpu) > * which covers idle and NOHZ full CPUs. > */ > if (!mcnt || (jiffies - last) > MAX_SAMPLE_AGE) > - goto fallback; > + return cpufreq_quick_get_min(cpu); > > return div64_u64((cpu_khz * acnt), mcnt); > - > -fallback: > - freq = cpufreq_quick_get(cpu); > - return freq ? freq : cpu_khz;
It looks to me like modifying cpufreq_quick_get) to return policy->min if policy->cur is 0 would work in a similar way, wouldn't it?
> } > > static int __init bp_init_aperfmperf(void) > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c > index 50bbc969ffe5..a0b24f61a5b0 100644 > --- a/drivers/cpufreq/cpufreq.c > +++ b/drivers/cpufreq/cpufreq.c > @@ -1796,6 +1796,24 @@ unsigned int cpufreq_quick_get_max(unsigned int cpu) > } > EXPORT_SYMBOL(cpufreq_quick_get_max); > > +/** > + * cpufreq_quick_get_min - return the min frequency for a given CPU > + * @cpu: CPU number > + */ > +unsigned int cpufreq_quick_get_min(unsigned int cpu) > +{ > + struct cpufreq_policy *policy = cpufreq_cpu_get(cpu); > + unsigned int ret_freq = 0; > + > + if (policy) { > + ret_freq = policy->min; > + cpufreq_cpu_put(policy); > + } > + > + return ret_freq; > +} > +EXPORT_SYMBOL(cpufreq_quick_get_min); > + > /** > * cpufreq_get_hw_max_freq - get the max hardware frequency of the CPU > * @cpu: CPU number > diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h > index 172ff51c1b2a..c74dcb5f9263 100644 > --- a/include/linux/cpufreq.h > +++ b/include/linux/cpufreq.h > @@ -220,6 +220,7 @@ static inline bool policy_is_shared(struct cpufreq_policy *policy) > unsigned int cpufreq_get(unsigned int cpu); > unsigned int cpufreq_quick_get(unsigned int cpu); > unsigned int cpufreq_quick_get_max(unsigned int cpu); > +unsigned int cpufreq_quick_get_min(unsigned int cpu); > unsigned int cpufreq_get_hw_max_freq(unsigned int cpu); > void disable_cpufreq(void); > > @@ -250,6 +251,10 @@ static inline unsigned int cpufreq_quick_get_max(unsigned int cpu) > { > return 0; > } > +static inline unsigned int cpufreq_quick_get_min(unsigned int cpu) > +{ > + return 0; > +} > static inline unsigned int cpufreq_get_hw_max_freq(unsigned int cpu) > { > return 0; > -- > 2.25.1 > >
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