[Pharo-project] Counting Messages as a Proxy for Average Execution Time in Pharo

Michael Haupt mhaupt at gmail.com
Thu Apr 28 23:35:19 CEST 2011


Hi Alex,

On 29 April 2011 00:08, Alexandre Bergel <alexandre.bergel at me.com> wrote:
>> I think you're being a bit harsh on stack sampling there. It is exact
>> enough to drive optimisation in some really high-performance VMs. It
>> is also deterministic enough to yield data leading to very good
>> performance results in those VMs. Whether focusing on counting
>> messages instead of taking samples is more beneficial would have to be
>> determined by experiment ...
>
> Yes, 25 pages of experiment :-)

oh, I was not referring to your paper. I was referring to the general
applicability of message counting as opposed to sampling. The latter
is true-and-tried in many high performance VMs. For the former, an
experiment has yielded good results (from what I take from this thread
- I still haven't read your paper, sorry, it's on top of the pile) in
a constrained setting. All I was saying is that it is not possible to
conclude anything for the broader area from the experiments you
conducted. But we're probably of the same opinion here.

>> What you mean with "non-portable" I do not understand.
>
> The information about the execution time contained in your profile cannot be compared with a new profile realized on a different machine, with a different CPU.

That is correct, but the approach itself is portable - may I quote
you: "Most profilers, including MessageTally, count stack frames at a
regular interval. This is doomed to be inexact, non-deterministic and
non-portable". You weren't talking about the results. Those are
obviously specific to the platform, clock frequency, L1/L2/L3 cache
and memory sizes, application input (!) and other factors.

Best,

Michael



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