Commit c0edbd4a authored Apr 16, 2017 by Chen Yu Committed by Thomas Gleixner Apr 20, 2017

x86/irq: Optimize free vector check in the CPU offline path



Before offlining a CPU its required to check whether there are enough free
irq vectors available so interrupts can be migrated away from the CPU.

This check is executed whether its required or not and neither stops
searching when the number of required free vectors are reached.

Bypass the free vector check if the current CPU has no irq to migrate and
leave the for_each_online_cpu() loop when the free vector count reaches the
number of required vectors.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Len Brown <lenb@kernel.orq>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Link: http://lkml.kernel.org/r/1492357410-510-1-git-send-email-yu.c.chen@intel.com


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

parent f61143c4

arch/x86/kernel/irq.c

+7 −2

Original line number	Diff line number	Diff line
		@@ -394,6 +394,9 @@ int check_irq_vectors_for_cpu_disable(void)
		!cpumask_subset(&affinity_new, &online_new))
		this_count++;
		}
		/* No need to check any further. */
		if (!this_count)
		return 0;

		count = 0;
		for_each_online_cpu(cpu) {
		@@ -411,8 +414,10 @@ int check_irq_vectors_for_cpu_disable(void)
		for (vector = FIRST_EXTERNAL_VECTOR;
		vector < first_system_vector; vector++) {
		if (!test_bit(vector, used_vectors) &&
		IS_ERR_OR_NULL(per_cpu(vector_irq, cpu)[vector]))
		count++;
		IS_ERR_OR_NULL(per_cpu(vector_irq, cpu)[vector])) {
		if (++count == this_count)
		return 0;
		}
		}
		}

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