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

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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>
This commit is contained in:
Chen Yu 2017-04-16 23:43:30 +08:00 committed by Thomas Gleixner
parent f61143c450
commit c0edbd4a16
1 changed files with 7 additions and 2 deletions
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9
arch/x86/kernel/irq.c
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@ -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;
}
}
}