linux-kernel - [PATCH 2/6] cleanup account_system_vtime with this_cpu

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Date:	Mon, 25 Oct 2010 15:30:13 -0700
From:	Venkatesh Pallipadi <venki@...gle.com>
To:	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>
Cc:	linux-kernel@...r.kernel.org, Paul Turner <pjt@...gle.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Shaun Ruffell <sruffell@...ium.com>,
	Yong Zhang <yong.zhang0@...il.com>,
	Venkatesh Pallipadi <venki@...gle.com>
Subject: [PATCH 2/6] cleanup account_system_vtime with this_cpu_* -v1

this_cpu_* variants are optimal than per_cpu(). Cleanup
IRQ_TIME_ACCOUNTING account_system_vtime to use this_cpu_*.

Signed-off-by: Venkatesh Pallipadi <venki@...gle.com>
---
 kernel/sched.c |   14 ++++++--------
 1 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index fae668b..a37bb83 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1966,7 +1966,6 @@ static u64 irq_time_cpu(int cpu)
 void account_system_vtime(struct task_struct *curr)
 {
 	unsigned long flags;
-	int cpu;
 	u64 now, delta;
 
 	if (!sched_clock_irqtime)
@@ -1974,20 +1973,19 @@ void account_system_vtime(struct task_struct *curr)
 
 	local_irq_save(flags);
 
-	cpu = smp_processor_id();
-	now = sched_clock_cpu(cpu);
-	delta = now - per_cpu(irq_start_time, cpu);
-	per_cpu(irq_start_time, cpu) = now;
+	now = sched_clock_cpu(smp_processor_id());
+	delta = now - this_cpu_read(irq_start_time);
+	this_cpu_write(irq_start_time, now);
 	/*
 	 * We do not account for softirq time from ksoftirqd here.
 	 * We want to continue accounting softirq time to ksoftirqd thread
 	 * in that case, so as not to confuse scheduler with a special task
 	 * that do not consume any time, but still wants to run.
 	 */
-	if (hardirq_count())
-		per_cpu(cpu_hardirq_time, cpu) += delta;
+	if (in_irq())
+		this_cpu_add(cpu_hardirq_time, delta);
 	else if (in_serving_softirq() && curr != this_cpu_ksoftirqd())
-		per_cpu(cpu_softirq_time, cpu) += delta;
+		this_cpu_add(cpu_softirq_time, delta);
 
 	local_irq_restore(flags);
 }
-- 
1.7.1

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