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Groups > linux.kernel > #1619496 > unrolled thread
| Started by | Chen Yu <yu.c.chen@intel.com> |
|---|---|
| First post | 2017-04-09 16:00 +0200 |
| Last post | 2017-04-10 13:30 +0200 |
| Articles | 2 — 2 participants |
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[PATCH] x86/irq: Do not check available vectors if current CPU has no irq to migrate Chen Yu <yu.c.chen@intel.com> - 2017-04-09 16:00 +0200
Re: [PATCH] x86/irq: Do not check available vectors if current CPU has no irq to migrate Prarit Bhargava <prarit@redhat.com> - 2017-04-10 13:30 +0200
| From | Chen Yu <yu.c.chen@intel.com> |
|---|---|
| Date | 2017-04-09 16:00 +0200 |
| Subject | [PATCH] x86/irq: Do not check available vectors if current CPU has no irq to migrate |
| Message-ID | <tulxL-3uX-1@gated-at.bofh.it> |
This is an optimization to bypass the free vector checking if the current
CPU has no irq to migrate. This can especially speed up the CPU offline
process when there are many CPUs in the system.
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Len Brown <len.brown@intel.com>
Cc: x86@kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
---
arch/x86/kernel/irq.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
index 4d8183b..b9bdc1e 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) {
--
2.7.4
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| From | Prarit Bhargava <prarit@redhat.com> |
|---|---|
| Date | 2017-04-10 13:30 +0200 |
| Subject | Re: [PATCH] x86/irq: Do not check available vectors if current CPU has no irq to migrate |
| Message-ID | <tuFGa-8rl-21@gated-at.bofh.it> |
| In reply to | #1619496 |
On 04/09/2017 09:53 AM, Chen Yu wrote:
> This is an optimization to bypass the free vector checking if the current
> CPU has no irq to migrate. This can especially speed up the CPU offline
> process when there are many CPUs in the system.
Chen, OOC how much time does this save?
P.
>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: Prarit Bhargava <prarit@redhat.com>
> Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
> Cc: Len Brown <len.brown@intel.com>
> Cc: x86@kernel.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Chen Yu <yu.c.chen@intel.com>
> ---
> arch/x86/kernel/irq.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
> index 4d8183b..b9bdc1e 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) {
>
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