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Date: Wed, 19 Aug 2009 00:57:46 +0900 (JST)
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From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: Zhaolei <zhaolei@cn.fujitsu.com>
Subject: Re: [RFC PATCH] Add timer-source of walltime for ftrace
Cc: kosaki.motohiro@jp.fujitsu.com, Steven Rostedt <rostedt@goodmis.org>,
       Frederic Weisbecker <fweisbec@gmail.com>, Ingo Molnar <mingo@elte.hu>,
       LKML <linux-kernel@vger.kernel.org>
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> +u64 notrace trace_clock_walltime(void)
> +{
> +	u32 remainder;
> +	return base_walltime.tv_sec + div_u64_rem(
> +			trace_clock() + base_walltime.tv_nsec,
> +			NSEC_PER_SEC, &remainder);
> +}

Why do we need calculate walltime at ring-buffer recordng phase?
IOW, Why can't we calculate this at displaing time?