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Re: [Xen-devel] PV guest timings

 Latency is the time between the deadline and the handler being called.
Ok, that's a reasonable definition of latency. However, if you don't
mind another question, 'deadline' here is basically the deadline of the
periodic instance x-1, and you expect a timer firing at that time in
order to activate instance x? Or is that a proper deadline (and the
above is just called period) and you want to have some handler running
when it's missed?
Each time the timer handler is called it calculates the deadline for the next handler and calls VCPUOP_set_singleshot_timer specifying the deadline. The deadline is calculated as the "previous deadline + the period". So handler instance 'n' will set the deadline for handler instance 'n+1' as "deadline n + period".
I'm not sure if that answers the question, but that is what is happening.
  Negative latency means the handler was called before the next
Oh, wow... I see. So you're saying that you have timers firing early
than their expiry time? Is that expected? Why is that happening? :-O
Yes. As I said I think this is the 100 Hz Hypervisor periodic timer. I need to be able to distinguish between the different timer interrupt sources.
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