Timer problems on FreeBSD 11R on KVM

[Allan Jude]

On 2017-03-01 12:46, Dmitry Marakasov wrote:
> 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?
> 

Look at:
kern.eventtimer.choice

and try different kern.eventtimer.timer values

-- 
Allan Jude

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