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SubjectRe: [PATCH] irq_balance does not make sense with HT but single physical CPU
On Wed, 26 Nov 2003, Kai Bankett wrote:

> this patch should disable irq_balance threat in case of only one
> installed physical cpu thats running in HyperThreading-mode (so reported
> as 2 cpus).
> I think it should make no sense to run irq_blanance in that special case
> - please correct me if i´m wrong.

+#ifdef CONFIG_X86_HT
+ /* On Hyper-Threading CPUs - if only one physical installed
+ balance does not make sense */
+ if (cpu_has_ht && smp_num_siblings == 2 && num_online_cpus() == 2) {
+ irqbalance_disabled = 1;
+ return 0;
+ }
+#endif

Further down, i believe the following would have the same effect;

/*
* Enable physical balance only if more than 1 physical processor
* is present
*/
if (smp_num_siblings > 1 && !cpus_empty(tmp))
physical_balance = 1;


tmp = cpu_online_map >> 2;

so we drop the first two processors (logical or physical) and only enable
physical balance if there are still processors present in the map. Or are
you observing something else?

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