linux-kernel - Re: [PATCH 0/3] Add walltime support for ring-buffer

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Date:	Mon,  3 Aug 2009 18:32:11 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	kosaki.motohiro@...fujitsu.com,
	Frederic Weisbecker <fweisbec@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Zhaolei <zhaolei@...fujitsu.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/3] Add walltime support for ring-buffer

> 
> * KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> wrote:
> 
> > It can. but I don't think it is sufficient. On flight recorder 
> > use-case, The tracing run more than one year. And, Administrator 
> > only see last N sec log. (previous logs were overwritten by 
> > ring-buffer go-around)
> 
> That's definitely something we want to enable ASAP.
> 
> I'm wondering why a single u64 timestamp is not enough to express 
> the full, absolute range of time elapsed since bootup, in 
> nanoseconds.
> 
> That would make walltime a matter of pretty-printing only - we'd 
> have to convert the u64 nsec timestamp into a walltime format, 
> right?
> 
> In fact we could change all the timestamps to be standardized along 
> 'nanoseconds elapsed since 1970' or so - not nanoseconds since the 
> last bootup. That still fits just fine within 64 bits - u64 
> nanoseconds has a scope of 500+ years.

Ah, you are right. thanks correct me.
but I think ntp updating time storing is necessary too.



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