FreeBSD-11.0-CURRENT on ARM: performance and load average

[Ian Lepore]

On Sun, 2014-09-21 at 01:04 +0400, Maxim V FIlimonov wrote:
> On Saturday 20 September 2014 13:24:08 Ian Lepore wrote:
> > Since it's happening only on that hardware, there's a good chance the
> > problem is in the allwinner a10/a20 clock driver, not in the general
> > eventtimer code.  In fact, looking at the code it appears that a
> > divide-by-16 is being set in the hardware, but not accounted for when
> > setting the frequency of the eventtimer.
> > 
> > Hmm, it should affect the timecounter too, in which case you'd see
> > time-of-day advancing 16x too fast.  If ntpd is running it would need to
> > step the clock pretty frequently, which would show up in syslog.
> > 
> 
> I'm running FreeBSD-current on the board right now, the time is just fine.
> 
> > I don't have hardware to test on, please see if the attached patch makes
> > a difference.
> > 
>  
> Well, it did: with the patch applied, the time ran about 60 times as fast as 
> it should have. I didn't notice any changes with load average, though: maybe 
> it's because I forgot to turn that sysctl setting I set before back to 0.
> 
> wbr, Maxim Filimonov
> che at bein.link

60 times as fast doesn't make much sense for changing a divisor to 16.

Without that patch, what is the output of

 sysctl kern.eventtimer
 sysctl kern.timecounter

If you repeatedly do "ntpdate -q <some server>" every 15 seconds for a
couple minutes, does the offset stay pretty much the same?  (like no big
changes in the first two decimal places)  Don't use a server like
pool.ntp.org where you might get a different server every time, instead
do "host pool.ntp.org" and pick one of the IPs and use it every time.

-- Ian