linux-kernel - Re: Re: [RFC PATCH] Add timer-source of walltime for ftrace

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Message-ID: <4A8BC301.3080404@cn.fujitsu.com>
Date:	Wed, 19 Aug 2009 17:16:49 +0800
From:	Zhaolei <zhaolei@...fujitsu.com>
To:	Steven Rostedt <rostedt@...dmis.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
CC:	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Re: [RFC PATCH] Add timer-source of walltime for ftrace

Steven Rostedt wrote:
> On Wed, 19 Aug 2009, KOSAKI Motohiro wrote:
> 
>>> +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?
> 
> Right! We should have something like this:
> 
> 	return (u64)base_walltime.tv_sec * NSEC_PER_SEC +
> 		trace_clock() + base_walltime.tv_nsec;
> 
> And then we could divide it out later.
> 
> And then we could even show more fields in the output and not limit 
> ourselves to seconds.
> 
> -- Steve

Hello, Steven, Kosaki-san:

Thanks for your good suggestion,
I'll fix it in next version.

Thanks
Zhaolei

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