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

[Ian Lepore]

On Sun, 2014-09-21 at 13:06 +0400, Maxim V FIlimonov wrote:
> On Saturday 20 September 2014 17:46:09 Ian Lepore wrote:
> > 
> > 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
> 
> Here it is:
> root at cubie:~ # sysctl kern.eventtimer
> kern.eventtimer.et.a10_timer Eventtimer.flags: 3
> kern.eventtimer.et.a10_timer Eventtimer.frequency: 24000000
> kern.eventtimer.et.a10_timer Eventtimer.quality: 1000
> kern.eventtimer.choice: a10_timer Eventtimer(1000)
> kern.eventtimer.singlemul: 4
> kern.eventtimer.idletick: 0
> kern.eventtimer.timer: a10_timer Eventtimer
> kern.eventtimer.periodic: 1
> root at cubie:~ # sysctl kern.timecounter
> kern.timecounter.tc.a10_timer timer0.mask: 4294967295
> kern.timecounter.tc.a10_timer timer0.counter: 4271639596
> kern.timecounter.tc.a10_timer timer0.frequency: 24000000
> kern.timecounter.tc.a10_timer timer0.quality: 1000
> kern.timecounter.stepwarnings: 0
> kern.timecounter.alloweddeviation: 5
> kern.timecounter.hardware: a10_timer timer0
> kern.timecounter.choice: a10_timer timer0(1000) dummy(-1000000)
> kern.timecounter.tick: 1
> kern.timecounter.fast_gettime: 1
> 
> 
> > 
> > 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.
> > 
> 
> root at cubie:~ # ntpdate time.nist.gov
> 21 Sep 13:04:55 ntpdate[2236]: adjust time server 24.56.178.140 offset 
> -0.117727 sec
> root at cubie:~ # ntpdate time.nist.gov
> 21 Sep 13:04:57 ntpdate[2237]: adjust time server 24.56.178.140 offset 
> -0.117018 sec
> root at cubie:~ # ntpdate time.nist.gov
> 21 Sep 13:05:00 ntpdate[2238]: adjust time server 24.56.178.140 offset 
> -0.116026 sec
> root at cubie:~ # ntpdate time.nist.gov
> 21 Sep 13:05:08 ntpdate[2241]: adjust time server 24.56.178.140 offset 
> -0.111525 sec
> root at cubie:~ # ntpdate time.nist.gov
> 21 Sep 13:05:26 ntpdate[2242]: adjust time server 24.56.178.140 offset 
> -0.103121 sec
> root at cubie:~ # ntpdate time.nist.gov
> 21 Sep 13:05:34 ntpdate[2243]: adjust time server 24.56.178.140 offset 
> -0.099055 sec
> 
> So as you could notice, the offset doesn't change much.

No, quite to the contrary, the time is changing rapidly -- it moved
about 19 milliseconds in 39 seconds, or roughly a millisecond every two
seconds.  That's an error rate of 500 parts per million, which is huge.
However, it's not off by a factor of 16, so that's a bit confusing.

BTW, time.nist.gov is not one server, it's a pool just like pool.ntp.org
(we run one of the time.nist.gov server installations out of our
building at $work).  I think it probably worked for you because of some
sort of dns caching effect, because you clearly kept getting the same
server each time.

-- Ian