[Speed] Analysis of a Python performance issue

[serge guelton]

On Sat, Nov 19, 2016 at 02:32:26AM +0100, Victor Stinner wrote:
> Hi,
> 
> I'm happy because I just finished an article putting the most
> important things that I learnt this year on the most silly issue with
> Python performance: code placement.
> 
> https://haypo.github.io/analysis-python-performance-issue.html
> 
> I explain how to debug such issue and my attempt to fix it in CPython.
> 
> I hate code placement issues :-) I hate performance slowdowns caused
> by random unrelated changes...
> 
> Victor

Thanks *a lot* victor for this great article. You not only very
accurately describe the method you used to track the performance bug,
but also give very convincing results.

I still wonder what the conclusion should be:

- (this) Micro benchmarks are not relevant at all, they are sensible to minor
  factors that are not relevant to bigger applications

- There is a generally good code layout that favors most applications?
  Maybe some core function from the interpreter ? Why does PGO fails to
  ``find'' them?

Serge