Commit-ID: c0edbd4a1693600d6eb9e2faad452638c35391f7 Gitweb: http://git.kernel.org/tip/c0edbd4a1693600d6eb9e2faad452638c35391f7 Author: Chen Yu <[email protected]> AuthorDate: Sun, 16 Apr 2017 23:43:30 +0800 Committer: Thomas Gleixner <[email protected]> CommitDate: Thu, 20 Apr 2017 15:25:09 +0200
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 <[email protected]> Signed-off-by: Chen Yu <[email protected]> Cc: Prarit Bhargava <[email protected]> Cc: Len Brown <[email protected]> Cc: "Rafael J. Wysocki" <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Thomas Gleixner <[email protected]> --- 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 4d8183b..f34fe74 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; + } } }
