Re: [XenPPC] performance profiling current and future steps

[Christian Ehrhardt <ehrhardt@xxxxxxxxxxxxxxxxxx>]

Jimi Xenidis wrote:
> ...
> > Part II
> > == Thoughts about the way to step 2 - profiling xen ==
> > ->the hypercall could now additionally pass a function pointer for a 
> > function in linux
> >  that handles xen perf interrupts
> hmm, we generally do not have that ability to specify a function that 
> Xen run in a domain, we could but I'm not sure it makes sense.  I 
> would think that we would use event channels exclusively for this and 
> the domain activity would be wired to an IRQ.
> Is that not how it works in the other architectures?
> Please expand on this "function pointer"
No function pointer passed via the hypercall - sorry about the confusion.
You're right, they use a shared buffer between the domain and xen. xen 
places the samples there and notifies the domain via an event channel. 
This leads to an interrupt in the guest which maps this interrupt to a 
function that reads the queued data and handles it.
When we are going to extend our solution to profile xen I hope we could 
use a similar approach to pass xen samples to the domain.
--

Grüsse / regards, 
Christian Ehrhardt
IBM Linux Technology Center, Open Virtualization
+49 7031/16-3385
Ehrhardt@xxxxxxxxxxxxxxxxxxx
Ehrhardt@xxxxxxxxxx

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