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From: John Baldwin <jhb@freebsd.org>
To: Jia-Shiun Li <jiashiun@gmail.com>
Cc: Konstantin Belousov <kostikbel@gmail.com>,
 freebsd-current <freebsd-current@freebsd.org>,
 Konstantin Belousov <kib@freebsd.org>
Subject: Re: TSC as timecounter makes system lag
Date: Fri, 24 Feb 2017 09:44:19 -0800
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On Friday, February 24, 2017 10:50:19 PM Jia-Shiun Li wrote:
> On Fri, Feb 24, 2017 at 9:32 PM, Jia-Shiun Li <jiashiun@gmail.com> wrote:
> 
> > On Fri, Feb 24, 2017 at 7:45 PM, Konstantin Belousov <kostikbel@gmail.com>
> > wrote:
> >
> >> On Fri, Feb 24, 2017 at 12:15:26PM +0800, Jia-Shiun Li wrote:
> >> > Tested working on E7400 against r313909. And changing timecounter
> >> from/to
> >> > TSC
> >> > correctly enables/disables C2.
> >> >
> >> > The latter part cpu_disable_c2_sleep++ is not needed. When
> >> > init_TSC_tc() got called timecounter is not yet tsc_timecounter.
> >> > inittimecounter() later will do the work calling tc_windup().
> >> >
> >>
> >> You mean, just this
> >> -       if (cpu_deepest_sleep >= 2 && cpu_vendor_id == CPU_VENDOR_INTEL &&
> >> +       if (cpu_vendor_id == CPU_VENDOR_INTEL &&
> >> is enough to fix the issue ?  If yes, we can remove the cpu_deepest_sleep
> >> variable.  This is John' observation, I think he would prefer to prepare
> >> the patch.
> >>
> >
> > Correct. That's enough.
> >
> >
> Since that's simple enough... patch attached.
> Tested against r313909 too.

Thanks for tracking down the cause and the patch!

-- 
John Baldwin