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SubjectRe: [numbers] perfmon/pfmon overhead of 17%-94%

* 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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