[PATCH 1/1] irq: Set CPU affinity soon after irq thread is created

[PATCH 1/1] irq: Set CPU affinity soon after irq thread is created

[Sankara Muthukrishnan]

From: Sankara S Muthukrishnan <sankara.m@ni.com>

As irq_thread_check_affinity is called ONLY inside the while loop in the
irq thread, the core affinity is set only when an interrupt occurs.
This patch sets the core affinity soon after the irq thread is created
and before it waits for interrupts. In real-tiime targets that do not
typically change the core affinity of irqs during run-time, this patch
will save additional latency of an irq thread in setting the core
affinity during the first interrupt occurrence for that irq.

Signed-off-by: Sankara S Muthukrishnan <sankara.m@ni.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
---
Hi Thomas,

As we discussed in the original thread
http://marc.info/?l=linux-kernel&m=134987001701683&w=2 , I am sending
this patch against the current mainline.

 kernel/irq/manage.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 4c69326..020b535 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -833,6 +833,8 @@ static int irq_thread(void *data)
 	init_task_work(&on_exit_work, irq_thread_dtor);
 	task_work_add(current, &on_exit_work, false);

+	irq_thread_check_affinity(desc, action);
+
 	while (!irq_wait_for_interrupt(action)) {
 		irqreturn_t action_ret;

-- 
1.7.11.4

[tip:irq/core] irq: Set CPU affinity right on thread creation

[tip-bot for Sankara Muthukrishnan]

Commit-ID:  f3de44edf376d18773febca6a37800c042bada7d
Gitweb:     http://git.kernel.org/tip/f3de44edf376d18773febca6a37800c042bada7d
Author:     Sankara Muthukrishnan <sankara.m@gmail.com>
AuthorDate: Wed, 31 Oct 2012 15:41:23 -0500
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Thu, 1 Nov 2012 12:11:31 +0100

irq: Set CPU affinity right on thread creation

As irq_thread_check_affinity is called ONLY inside the while loop in
the irq thread, the core affinity is set only when an interrupt
occurs. This patch sets the core affinity right after the irq thread
is created and before it waits for interrupts. In real-tiime targets
that do not typically change the core affinity of irqs during
run-time, this patch will save additional latency of an irq thread in
setting the core affinity during the first interrupt occurrence for
that irq.

Signed-off-by: Sankara S Muthukrishnan <sankara.m@ni.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/CAFQPvXeVZ858WFYimEU5uvLNxLDd6bJMmqWihFmbCf3ntokz0A@mail.gmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 kernel/irq/manage.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index d06a396..1cbd572 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -849,6 +849,8 @@ static int irq_thread(void *data)
 	init_task_work(&on_exit_work, irq_thread_dtor);
 	task_work_add(current, &on_exit_work, false);
 
+	irq_thread_check_affinity(desc, action);
+
 	while (!irq_wait_for_interrupt(action)) {
 		irqreturn_t action_ret;