Messages in this thread | | | Date | Tue, 20 Jul 2010 11:57:03 -1000 | From | Zachary Amsden <> | Subject | Re: [PATCH 04/18] Make cpu_tsc_khz updates use local CPU |
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On 07/19/2010 10:53 PM, Avi Kivity wrote: > On 07/19/2010 11:06 PM, Zachary Amsden wrote: >>>> +static void tsc_khz_changed(void *data) >>>> { >>>> - /* nothing */ >>>> + struct cpufreq_freqs *freq = data; >>>> + unsigned long khz = 0; >>>> + >>>> + if (data) >>>> + khz = freq->new; >>>> + else if (!boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) >>>> + khz = cpufreq_quick_get(raw_smp_processor_id()); >>>> + if (!khz) >>>> + khz = tsc_khz; >>>> + __get_cpu_var(cpu_tsc_khz) = khz; >>>> } >>> >>> Do we really need to cache cpufreq_quick_get()? If it's really >>> quick, why not just use it everywhere instead of cacheing it? Not a >>> comment on this patch. >>> >> >> >> If cpufreq is compiled in, but disabled, it returns zero, so we need >> some sort of logic. > > Maybe it's better to put it into cpufreq_quick_get(). Inconsistent > APIs that appear to work are bad. >
I don't think it's quite so simple; cpufreq is platform independent and tsc_khz is a platform specific export. It seems cpufreq is designed to return zero when disabled and we're the unusual ones for wanting to use it.
Zach
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