Messages in this thread | | | Date | Tue, 9 Feb 2010 09:54:43 +0300 | Subject | Re: [RFC perf,x86] P4 PMU early draft | From | Cyrill Gorcunov <> |
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On 2/9/10, Ingo Molnar <mingo@elte.hu> wrote: > > * Cyrill Gorcunov <gorcunov@gmail.com> wrote: > >> Hi all, >> >> first of all the patches are NOT for any kind of inclusion. It's not ready >> >> yet. More likely I'm asking for glance review, ideas, criticism. > > A quick question: does the code produce something on a real P4? (possibly > only running with a single event - but even that would be enough.)
not yet, a few code snippets need to be added into scheduling routine, hope to finish this today evening
> >> The main problem in implementing P4 PMU is that it has much more >> restrictions for event to MSR mapping. [...] > > One possibly simpler approach might be to represent the P4 PMU via a maximum > _two_ generic events only. >
yeah, good idea!
> Last i looked at the many P4 events, i've noticed that generally you can > create any two events. (with a few exceptions) Once you start trying to take > advantage of the more than a dozen seemingly separate counters, additional > non-trivial constraints apply. > > So if we only allowed a maximum of _two_ generic events (like say a simple > Core2 has, so it's not a big restriction at all), we wouldnt have to map all > the constraints, we'd only have to encode the specific event-to-MSR details. > (which alone is quite a bit of work as well.) > > We could also use the new constraints code to map them all, of course - it > will certainly be more complex to implement. >
i thought about it, but i didn't like the result code ;) will think about it.
> Hm? > > Ingo >
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