Re: [Xen-devel] PV timer issues in FreeBSD

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 19.04.13 at 20:20, Roger Pau MonnÃ<roger.pau@xxxxxxxxxx> wrote:
> While trying to get PV timers on FreeBSD to work, we found that when the
> system is under stress sometimes FreeBSD would stop receiving timer
> interrupts on certain vCPUs. I've added some trace points to Xen in
> order to see what was happening with this timers and got the following
> trace. I'm also attaching the crappy changes I've did to Xen in order to
> add the trace points, maybe I didn't put the trace points in the right
> position and that's why I'm seeing this:

For those of us not familiar with FreeBSD - which interrupt is it
using as timer interrupt (IRQ0, LAPIC, HPET, RTC)?

Considering that you had problems with the RTC running FreeBSD
on unstable, I'm particularly wondering whether there is still an
issue left, even more so as I think that the 10-instance grace
period for not shutting down the periodic interrupt may be too
small when the system is under stress and the period is rather
short (I'm thinking that the period should really be dependent on
vCPU execution time, not absolute [host] time, as a mostly
stalled - due to higher priority load - vCPU may not even have a
chance to get its interrupt handler to run).

Jan

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