Re: [PATCH v6 1/4] sched/clock: interface to allow timestamps early in boot

[Dou Liyang]

Hi, Pasha

At 09/28/2017 09:11 PM, Pasha Tatashin wrote:
> > > > It will be best if we can support TSC sync capability in x86, but seems
> > > > is not easy.
> > >
> > > Sure, your hardware achieving sync would be best, but even if it does
> > > not, we can still use TSC. Using notsc simple because you fail to sync
> > > TSCs is quite crazy.
> > >
> > > The thing is, we need to support unsync'ed TSC in any case, because
> > > older chips (pre Nehalem) didn't have synchronized TSC in any case, and
> > > it still happens on recent chips if the BIOS mucks it up, which happens
> > > surprisingly often :-(
> > >
> > > I would suggest you try your reconfigurable setup with "tsc=unstable"
> > > and see if that works for you. That marks the TSC unconditionally
> > > unstable at boot and avoids any further wobbles once the TSC watchdog
> > > notices (although that too _should_ more or less work).
> >
> > That should do the trick nicely and we might just end up converting notsc
> > to tsc=unstable silently so we can avoid the bike shed discussions about
> > removing it.
>
> Ok, I will start working on converting notsc to unstable, and modify my
> patches to do what Peter suggested earlier. In the mean time, I'd like
> to hear from Dou if this setup works with dynamic reconfig.

OK, I will do it, But, October 1 is our national holiday, I will in 
holiday, and I just returned the test machine. :-(

May reply you in middle of the October.

Thanks,

	dou.

> Thank you,
> Pasha