Re: [patch 54/55] timekeeping: Provide fast and NMI safe access to CLOCK_MONOTONIC[_RAW]

[Thomas Gleixner]

On Mon, 14 Jul 2014, Mathieu Desnoyers wrote:

> ----- Original Message -----
> > From: "Peter Zijlstra" <peterz@xxxxxxxxxxxxx>
> > To: "Thomas Gleixner" <tglx@xxxxxxxxxxxxx>
> > Cc: "LKML" <linux-kernel@xxxxxxxxxxxxxxx>, "John Stultz" <john.stultz@xxxxxxxxxx>, "Steven Rostedt"
> > <rostedt@xxxxxxxxxxx>, "Mathieu Desnoyers" <mathieu.desnoyers@xxxxxxxxxxxx>
> > 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 ...
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