Re: [PATCH 04/18] Make cpu_tsc_khz updates use local CPU

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



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
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html


[Index of Archives]     [KVM ARM]     [KVM ia64]     [KVM ppc]     [Virtualization Tools]     [Spice Development]     [Libvirt]     [Libvirt Users]     [Linux USB Devel]     [Linux Audio Users]     [Yosemite Questions]     [Linux Kernel]     [Linux SCSI]     [XFree86]
  Powered by Linux