Re: [Xen-devel] /proc/interrupts on unprivileged domains

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

> Hi everyone,
> 
> I'm trying to understand the values in /proc/interrupts of
> unprivileged domains. Specifically, I'm interested in the value of the
> timer interrupt. AFAIK, this value reflects the number of times this
> domain received the timer interrupt from Xen? Equivalently, the number
> of times the timer_interrupt() function (and thus the
> do_timer_interrupt) function of the guest OS (linux, in this case)
> were called? Please correct me if I'm wrong.

All correct.

> If that is indeed the case, then my real curiosity is this -- what
> parameters affect this number? Again, AFAIK Xen gives a timer
> interrupt periodically to a currently running domain, and also when a
> domain gets scheduled.

Xen gives a domain an interrupt every 10ms while it runs, and every
time the domain is rescheduled. It also gives an interrupt whenever
the domain's prgrammable one-shot timer expires (used by Linux to set
an appropriate  timeout whenever it blocks).

> But how does this indirectly depend on other
> parameters -- like the cpu frequency, the system time, the tsc
> timestamp value and so on.

It doesn't. :-)

 -- Keir


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