linux-kernel - Re: [RFC patch 15/15] LTTng timestamp x86

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Message-ID: <48FD0633.70604@zytor.com>
Date:	Mon, 20 Oct 2008 15:29:07 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	john stultz <johnstul@...ibm.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	"Luck, Tony" <tony.luck@...el.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>,
	David Miller <davem@...emloft.net>,
	Ingo Molnar <mingo@...hat.com>
Subject: Re: [RFC patch 15/15] LTTng timestamp x86

Linus Torvalds wrote:
> 
> But it's not going to solve the "hey, I have 512 CPU's, they are all on 
> different boards, and no, they are _not_ synchronized to one global 
> clock!".
> 
> That's why I'd suggest making _purely_ local time, and then aiming for 
> something NTP-like. But maybe there are better solutions out there.
> 

At the same time, it would definitely be nice to encourage vendors of 
large SMP systems to provide a common root crystal (frequency standard) 
for a single SMP domain.  Preferrably a really good one, TCXO or better.

	-hpa
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