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List:       freebsd-hackers
Subject:    Re: [RFC] Enabling invariant TSC timecounter on SMP
From:       Jung-uk Kim <jkim () freebsd ! org>
Date:       2011-05-31 20:16:26
Message-ID: 201105311616.31256.jkim () FreeBSD ! org
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On Tuesday 31 May 2011 07:18 am, Andriy Gapon wrote:
> on 24/05/2011 20:56 Jung-uk Kim said the following:
> > I think it's about time to enable invariant TSC timecounter on
> > SMP by default.  Please see the attached patch.  It is also
> > available from here:
> >
> > http://people.freebsd.org/~jkim/tsc_smp_test4.diff
> >
> > avg convinced me enough that it should be an opt-out feature
> > going forward. :-)
>
> Not sure if I really did that.
> My position is this:
> - if we think that TSC is SMP-safe then it should have the best
> priority
> - we should do our best to auto-guess if TSC is SMP-safe 
> unless a user explicitly overrides that property (either via
> explicit testing or by making guesses based on CPU model or etc)

I am sorry if I misunderstood your intention.  However, I added 
explicit boot-time TSC sanity check (to do our best to auto-guess) 
and I think TSC is fairly SMP-safe.  Hence, I thought that it is 
about time for the change.

> > Comments?
>
> Perhaps I missed it, but I don't remember the "lowres" part of the
> patch being discussed.

No, it wasn't discussed with you.  Do you see any problem with that 
code?

Thanks,

Jung-uk Kim
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