From acba7889a77f29c3ed9e8d73d4a3e6d9655a7ade Mon Sep 17 00:00:00 2001 From: Chen Yu Date: Sun, 16 Apr 2017 23:43:30 +0800 Subject: [PATCH] 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 Signed-off-by: Chen Yu Cc: Prarit Bhargava Cc: Len Brown Cc: "Rafael J. Wysocki" Link: http://lkml.kernel.org/r/1492357410-510-1-git-send-email-yu.c.chen@intel.com Signed-off-by: Thomas Gleixner --- arch/x86/kernel/irq.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c index 4d8183b5f1132..f34fe7444836a 100644 --- a/arch/x86/kernel/irq.c +++ b/arch/x86/kernel/irq.c @@ -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; + } } } -- 2.39.5