Messages in this thread | | | Date | Tue, 19 Jun 2018 11:08:46 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [RFC PATCH 5/8] x86/umwait.c: Add sysfs interface to show tsc_khz |
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On Fri, 15 Jun 2018, Fenghua Yu wrote:
> +static ssize_t tsc_khz_show(struct device *dev, struct device_attribute *attr, > + char *buf) > +{ > + return sprintf(buf, "%d\n", tsc_khz); > +} > + > static DEVICE_ATTR_RW(umwait_disable_c0_2); > +static DEVICE_ATTR_RO(tsc_khz);
The right place to expose that information is the VDSO and a helper function which allows to convert from nsec to TSC.
> static struct attribute *umwait_attrs[] = { > &dev_attr_umwait_disable_c0_2.attr, > @@ -92,6 +100,15 @@ static int __init umwait_init(void) > if (ret) > return ret; > > + /* Only add the tsc_khz interface when the value is known. */
Why so? The only reason why you don't want to expose TSC frequency is when it's not constant frequency.
> + if (boot_cpu_has(X86_FEATURE_TSC_KNOWN_FREQ)) {
Thanks,
tglx
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