linux-kernel - [PATCH] Optimise tick_nohz_stop_sched

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Message-Id: <200802281510.51191.fzu@wemgehoertderstaat.de>
Date:	Thu, 28 Feb 2008 15:10:50 +0100
From:	Karsten Wiese <fzu@...gehoertderstaat.de>
To:	linux-kernel@...r.kernel.org
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>
Subject: [PATCH] Optimise tick_nohz_stop_sched_tick() a bit


Call
	ts = &per_cpu(tick_cpu_sched, cpu);
and
	cpu = smp_processor_id();
once instead of twice.

No functional change done, as changed code runs with local irq off.
Reduces source lines and text size (20bytes on x86_64).

Signed-off-by: Karsten Wiese <fzu@...gehoertderstaat.de>
---
 kernel/time/tick-sched.c |    6 ++----
 1 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 686da82..851a852 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -158,9 +158,8 @@ void tick_nohz_stop_idle(int cpu)
 	}
 }
 
-static ktime_t tick_nohz_start_idle(int cpu)
+static ktime_t tick_nohz_start_idle(int cpu, struct tick_sched *ts)
 {
-	struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
 	ktime_t now, delta;
 
 	now = ktime_get();
@@ -201,8 +200,8 @@ void tick_nohz_stop_sched_tick(void)
 	local_irq_save(flags);
 
 	cpu = smp_processor_id();
-	now = tick_nohz_start_idle(cpu);
 	ts = &per_cpu(tick_cpu_sched, cpu);
+	now = tick_nohz_start_idle(cpu, ts);
 
 	/*
 	 * If this cpu is offline and it is the one which updates
@@ -222,7 +221,6 @@ void tick_nohz_stop_sched_tick(void)
 	if (need_resched())
 		goto end;
 
-	cpu = smp_processor_id();
 	if (unlikely(local_softirq_pending())) {
 		static int ratelimit;
 
-- 
1.5.3.3
--
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