Re: PHP performance on Xen domU with mulitple vcpu

[Emmanuel Dreyfus <manu%netbsd.org@localhost>]

The problem strikes after 22 days (two vcpu, xen_system_time timecounter)
ntpd is unable to sync. If I run it aster a rdate, ntpq -c peers shows 
offset quickly climbing to 6000 in a few seconds, then 49000 after a minute.
 This is a mess.

I have a test program that calls gettimeofday 1000 times in a row
and count how many time it got the same value. I thought it is a 
good measure of the problem.
587 1746147362.737757
37 1746147362.747723
376 1746147362.747724

Switching to clockinterrupt timecounter is even worse: the clock
does not change when called 1000 times in a row.

I tried cpuctl offline 1, no change
cpuctl online 1; cpuctl offline 0 seems to restore clock sanity. 
My test shows that gettimeofday now returns a different value on 
each call. But ntpd still drifts a lot and is unable to sync.

     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
 timeserver1    145.238.80.80    2 u   12   64    3    0.344  +32825. 29231.6
 timeserver2    192.168.82.20    3 u   12   64    3    3.947  +32827. 28551.0

After reboot, everything is fine again.
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
 timeserver1   145.238.80.80    2 u   36   64    1    0.236   -0.119   0.024
*timeserver2   192.168.82.20    3 u   14   64    3    1.487   +0.585   0.133



-- 
Emmanuel Dreyfus
manu%netbsd.org@localhost