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From: Shan Wei <shanwei88@gmail.com>
To: rostedt@goodmis.org, fweisbec@gmail.com, mingo@redhat.com,
	Kernel-Maillist <linux-kernel@vger.kernel.org>,
	Christoph Lameter <cl@linux.com>
Subject: [PATCH] trace: use __this_cpu_inc/dec operation instead of __get_cpu_var
Date: Mon, 19 Nov 2012 13:21:01 +0800	[thread overview]
Message-ID: <50A9C1BD.1060308@gmail.com> (raw)

From: Shan Wei <davidshan@tencent.com>

__this_cpu_inc_return() or __this_cpu_dec generates a single instruction,
which is faster than __get_cpu_var operation.

Signed-off-by: Shan Wei <davidshan@tencent.com>
---
 kernel/trace/trace.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 18c0aa8..3795694 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1313,7 +1313,7 @@ static void __ftrace_trace_stack(struct ring_buffer *buffer,
 	 */
 	preempt_disable_notrace();
 
-	use_stack = ++__get_cpu_var(ftrace_stack_reserve);
+	use_stack = __this_cpu_inc_return(ftrace_stack_reserve);
 	/*
 	 * We don't need any atomic variables, just a barrier.
 	 * If an interrupt comes in, we don't care, because it would
@@ -1367,7 +1367,7 @@ static void __ftrace_trace_stack(struct ring_buffer *buffer,
  out:
 	/* Again, don't let gcc optimize things here */
 	barrier();
-	__get_cpu_var(ftrace_stack_reserve)--;
+	__this_cpu_dec(ftrace_stack_reserve);
 	preempt_enable_notrace();
 
 }
-- 
1.7.1


             reply	other threads:[~2012-11-19  5:21 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-11-19  5:21 Shan Wei [this message]
2012-11-19 21:34 ` [PATCH] trace: use __this_cpu_inc/dec operation instead of __get_cpu_var Christoph Lameter
2012-11-30  6:37 ` Shan Wei
2013-02-03 19:18 ` [tip:perf/core] tracing: Use __this_cpu_inc/ dec " tip-bot for Shan Wei

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