Timer problems on FreeBSD 11R on KVM

[Dmitry Marakasov]

Hi!

I'm running a bunch of FreeBSD VMs on VPS provider which uses KVM.
Recently one of them began bahaving strangely. Symptoms:

- Much ~(30%) CPU spent in intr
- top shows CPU used by "intr{swi4: clock (0)}"
- kernel: calcru: runtime went backwards from 13958 usec to 10792 usec for pid 919 (sshd)
  messages in logs
- There's no much load, no high network traffic, systat shows no excess
  interrupts.
- This intr load is sporadic in form of ~30 minute busts each several
  hours
- The box had ntpd running, but disabling it doesn't help
- Playing with timer-related sysctls does not help either

I've tried i8254 and TSC-low timecounters:

kern.timecounter.hardware: ACPI-fast
kern.timecounter.choice: TSC-low(800) i8254(0) ACPI-fast(900) dummy(-1000000)

and kern.eventtimer.periodic=1

to no effect.


I suspect that this began after some changes on the hoster's side.

- This VM was working for more than a year without problems before
- A graph which monitors a reply time of website running on that VM
  showed min. response time jump from 50 to 75 msec on Monday, after
  which problems began.

So while I'm getting the hoster to tell me what they have changed, any
ideas?

-- 
Dmitry Marakasov   .   55B5 0596 FF1E 8D84 5F56  9510 D35A 80DD F9D2 F77D
amdmi3 at amdmi3.ru  ..:  jabber: amdmi3 at jabber.ru      http://amdmi3.ru