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Date: Mon, 14 Jul 2014 16:15:35 +0200 (CEST)
From: Thomas Gleixner <tglx@linutronix.de>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
cc: Peter Zijlstra <peterz@infradead.org>, LKML <linux-kernel@vger.kernel.org>,
        John Stultz <john.stultz@linaro.org>,
        Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [patch 54/55] timekeeping: Provide fast and NMI safe access to
 CLOCK_MONOTONIC[_RAW]
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On Mon, 14 Jul 2014, Mathieu Desnoyers wrote:

> ----- Original Message -----
> > From: "Peter Zijlstra" <peterz@infradead.org>
> > To: "Thomas Gleixner" <tglx@linutronix.de>
> > Cc: "LKML" <linux-kernel@vger.kernel.org>, "John Stultz" <john.stultz@linaro.org>, "Steven Rostedt"
> > <rostedt@goodmis.org>, "Mathieu Desnoyers" <mathieu.desnoyers@efficios.com>
> > Sent: Monday, July 14, 2014 5:47:50 AM
> > Subject: Re: [patch 54/55] timekeeping: Provide fast and NMI safe access to CLOCK_MONOTONIC[_RAW]
> > 
> > On Fri, Jul 11, 2014 at 01:45:19PM -0000, Thomas Gleixner wrote:
> > > +static struct tk_fast tk_fast_raw  ____cacheline_aligned;
> > > +static struct tk_fast tk_fast_mono ____cacheline_aligned;
> > 
> > Question to the 'trace maniacs'; why do you lot need access to mono_raw?
> > 
> > I would much prefer to limit choice here.
> 
> For LTTng, which I guess qualifies as bring part of the aforementioned
> trace maniacs group, we only need the "tk_fast_mono" clock. We don't
> need mono_raw.
> 
> We can then correlate with user-space traces by using tk_fast_mono in
> kernel-space and using CLOCK_MONOTONIC in userspace.

I'm happy to ditch the raw one ...