Re: TSC vs. HPET timecounter priority

[yamt%mwd.biglobe.ne.jp@localhost (YAMAMOTO Takashi)]

hi,

> On Sun, Aug 12, 2012 at 08:14:50PM -0700, Erik Fair wrote:
> [..]
> 
>> Until something is written and committed, I suggest an easy change in 
>> timecounter
>> "quality" for HPET to make it preferred to TSC if both are present.
> 
> It took me also a little while to recognize that i have a timecounter issue.
> There was no error message from the ntpd that the system has not a stable
> clock. Another system didn't syncronize the time with ntp and so i had to
> hunt down what is wrong. My resolution was to change sysctl.conf to switch
> from tsc to hpet but that takes to find the issue.
> 
> What about the following patch?
> tc_quality for hpet is set to 2000 so it would have a higher priority.
> Using 1500 leave some room for other implementations to have a higher
> priority then tsc.

please take a look at tsc_tc_init.

YAMAMOTO Takashi

> 
> Index: tsc.c
> ===================================================================
> RCS file: /cvsroot/src/sys/arch/x86/x86/tsc.c,v
> retrieving revision 1.30
> diff -b -u -r1.30 tsc.c
> --- tsc.c     8 Aug 2011 17:00:23 -0000       1.30
> +++ tsc.c     13 Aug 2012 05:48:41 -0000
> @@ -59,7 +59,7 @@
>       .tc_get_timecount = tsc_get_timecount,
>       .tc_counter_mask = ~0U,
>       .tc_name = "TSC",
> -     .tc_quality = 3000,
> +     .tc_quality = 1500,
>  };
>  
>  void
> 
> Bernd
> 
>