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

Alexandre Bergel alexandre.bergel at me.com
Fri Apr 29 00:40:45 CEST 2011



On 28 Apr 2011, at 17:35, Michael Haupt wrote:

> 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

Alexandre Bergel  http://www.bergel.eu

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