Messages in this thread | | | Date | Tue, 30 Jun 2009 01:55:00 +0200 | From | Ingo Molnar <> | Subject | Re: [numbers] perfmon/pfmon overhead of 17%-94% |
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* Vince Weaver <vince@deater.net> wrote:
>> Besides, you compare perfcounters to perfmon > > what else shoud I be comparing it to? > >> (which you seem to be a contributor of) > > is that not allowed?
Here's the full, uncropped sentence i wrote:
" Besides, you compare perfcounters to perfmon (which you seem to be a contributor of), while in reality perfmon has much, much worse (and unfixable, because designed-in) measurement overhead. "
Where i question the blatant hypocracy of bringing up perfmon as a good example while in reality perfmon has far worse measurement overhead than perfcounters, for a wide range of workloads.
As far as i can see you didnt answer my questions: why are you dismissing perfcounters for a minor, once per startup measurement offset (which is entirely fixable - see the patch i sent), while you generously allow perfmon to have serious, 90% measurement overhead amounting to billions of instructions overhead per second, for certain workloads?
Ingo
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