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: Re: [PATCH] trace: use __this_cpu_inc/dec operation instead of __get_cpu_var
Date: Fri, 30 Nov 2012 14:37:32 +0800 [thread overview]
Message-ID: <50B8542C.3010109@gmail.com> (raw)
In-Reply-To: <50A9C1BD.1060308@gmail.com>
ping ......
Shan Wei said, at 2012/11/19 13:21:
> 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();
>
> }
>
next prev parent reply other threads:[~2012-11-30 6:37 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-19 5:21 [PATCH] trace: use __this_cpu_inc/dec operation instead of __get_cpu_var Shan Wei
2012-11-19 21:34 ` Christoph Lameter
2012-11-30 6:37 ` Shan Wei [this message]
2013-02-03 19:18 ` [tip:perf/core] tracing: Use __this_cpu_inc/ dec " tip-bot for Shan Wei
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