linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
* [PATCH] x86/irq: Do not check available vectors if no irq to migrate or required slots has been found
@ 2017-04-16 15:43 Chen Yu
  2017-04-20 13:30 ` [tip:x86/irq] x86/irq: Optimize free vector check in the CPU offline path tip-bot for Chen Yu
  0 siblings, 1 reply; 2+ messages in thread
From: Chen Yu @ 2017-04-16 15:43 UTC (permalink / raw)
  To: Yu Chen
  Cc: Thomas Gleixner, Ingo Molnar, H. Peter Anvin, Prarit Bhargava,
	Rafael J. Wysocki, Len Brown, x86, linux-kernel

A micro optimization to bypass the free vector checking if the current
CPU has no irq to migrate, also breaks the for_each_online_cpu() loop
when the count reaches the required vectors.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
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" <rjw@rjwysocki.net>
Cc: Len Brown <lenb@kernel.orq>
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 | 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;
+			}
 		}
 	}
 
-- 
2.7.4

^ permalink raw reply related	[flat|nested] 2+ messages in thread

* [tip:x86/irq] x86/irq: Optimize free vector check in the CPU offline path
  2017-04-16 15:43 [PATCH] x86/irq: Do not check available vectors if no irq to migrate or required slots has been found Chen Yu
@ 2017-04-20 13:30 ` tip-bot for Chen Yu
  0 siblings, 0 replies; 2+ messages in thread
From: tip-bot for Chen Yu @ 2017-04-20 13:30 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: hpa, mingo, yu.c.chen, tglx, lenb, prarit, linux-kernel, rjw

Commit-ID:  c0edbd4a1693600d6eb9e2faad452638c35391f7
Gitweb:     http://git.kernel.org/tip/c0edbd4a1693600d6eb9e2faad452638c35391f7
Author:     Chen Yu <yu.c.chen@intel.com>
AuthorDate: Sun, 16 Apr 2017 23:43:30 +0800
Committer:  Thomas Gleixner <tglx@linutronix.de>
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 <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>

---
 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;
+			}
 		}
 	}
 

^ permalink raw reply related	[flat|nested] 2+ messages in thread

end of thread, other threads:[~2017-04-20 13:32 UTC | newest]

Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2017-04-16 15:43 [PATCH] x86/irq: Do not check available vectors if no irq to migrate or required slots has been found Chen Yu
2017-04-20 13:30 ` [tip:x86/irq] x86/irq: Optimize free vector check in the CPU offline path tip-bot for Chen Yu

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).