Subject: Re: 2.6.14-rt13
From: Lee Revell <rlrevell@joe-job.com>
To: Fernando Lopez-Lezcano <nando@ccrma.Stanford.EDU>
Cc: Ingo Molnar <mingo@elte.hu>, linux-kernel@vger.kernel.org,
       "Paul E. McKenney" <paulmck@us.ibm.com>, "K.R. Foley" <kr@cybsft.com>,
       Steven Rostedt <rostedt@goodmis.org>,
       Thomas Gleixner <tglx@linutronix.de>, pluto@agmk.net,
       john cooper <john.cooper@timesys.com>,
       Benedikt Spranger <bene@linutronix.de>,
       Daniel Walker <dwalker@mvista.com>,
       Tom Rini <trini@kernel.crashing.org>,
       George Anzinger <george@mvista.com>
In-Reply-To: <1132336954.20672.11.camel@cmn3.stanford.edu>
References: <20051115090827.GA20411@elte.hu>
	 <1132336954.20672.11.camel@cmn3.stanford.edu>
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Date: Fri, 18 Nov 2005 16:54:41 -0500
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On Fri, 2005-11-18 at 10:02 -0800, Fernando Lopez-Lezcano wrote:
> You mentioned before that the TSC's from both cpus could drift from
> each other over time. Assuming that is the source of timing (I have no
> idea) that could explain the behavior of Jack, it gets a reference
> time from one of the cpus and then compares that with what it gets
> from either cpu depending on where it is running at a given time. If
> it is the same cpu all is fine, if it is the other and it has drifted
> then the warning is printed.  

Yes, JACK uses rdtsc() for microsecond resolution timing and assumes
that the TSCs are in sync.

I've asked on this list what a better time source could be and didn't
get any useful responses, people just told me "use gettimeofday()" which
is WAY too slow.

Lee

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