linux-kernel - [PATCH 2/2] perf, cpu hotplug: Use cached value of smp_processor

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Date:	Thu, 13 Sep 2012 20:12:26 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	a.p.zijlstra@...llo.nl, acme@...radead.org
Cc:	mingo@...nel.org, paulus@...ba.org, linux-kernel@...r.kernel.org,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
Subject: [PATCH 2/2] perf, cpu hotplug: Use cached value of smp_processor_id()

The perf_cpu_notifier() macro invokes smp_processor_id() multiple
times. Optimize it by using a local variable.

Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
---

 include/linux/perf_event.h |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index cc4574d..5b5b017 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1346,15 +1346,16 @@ static inline void perf_event_task_tick(void)				{ }
 do {									\
 	static struct notifier_block fn##_nb __cpuinitdata =		\
 		{ .notifier_call = fn, .priority = CPU_PRI_PERF };	\
+	unsigned long cpu = smp_processor_id();				\
 	unsigned long flags;						\
 	fn(&fn##_nb, (unsigned long)CPU_UP_PREPARE,			\
-		(void *)(unsigned long)smp_processor_id());		\
+		(void *)(unsigned long)cpu);				\
 	local_irq_save(flags);						\
 	fn(&fn##_nb, (unsigned long)CPU_STARTING,			\
-		(void *)(unsigned long)smp_processor_id());		\
+		(void *)(unsigned long)cpu);				\
 	local_irq_restore(flags);					\
 	fn(&fn##_nb, (unsigned long)CPU_ONLINE,				\
-		(void *)(unsigned long)smp_processor_id());		\
+		(void *)(unsigned long)cpu);				\
 	register_cpu_notifier(&fn##_nb);				\
 } while (0)
 

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