Date: Wed, 26 Nov 2003 10:46:25 -0500 (EST)
From: Zwane Mwaikambo <zwane@arm.linux.org.uk>
To: Kai Bankett <kbankett@aol.com>
cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] irq_balance does not make sense with HT but single
 physical CPU
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Message-ID: <Pine.LNX.4.58.0311261042540.1683@montezuma.fsmlabs.com>
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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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