+1 Alexandre
On 28 Apr 2011, at 17:35, Michael Haupt wrote: > Hi Alex, > > On 29 April 2011 00:08, Alexandre Bergel <[email protected]> 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 ^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;.
