[Python-Dev] Help requested with Python 2.7 performance regression

[Antoine Pitrou]

On Wed, 1 Mar 2017 12:28:24 -0500
Barry Warsaw <barry at python.org> wrote:
> 
> Louis (Cc'd here) has done a ton of work to measure and analyze the problem,
> but we've more or less hit a roadblock, so we're taking the issue public to
> see if anybody on this mailing list has further ideas.  A detailed analysis is
> available in this Google doc:
> 
> https://docs.google.com/document/d/1zrV3OIRSo99fd2Ty4YdGk_scmTRDmVauBprKL8eij6w/edit
> 
> The document should be public for comments and editing.

I may be misunderstanding the document, but this lacks at least a
comparison of the *same* interpreter version with different compiler
versions.

As for the high level: what if the training set used for PGO in Xenial
has become skewed or inadequate?  Just a thought, as it would imply
that PGO+LTO uses wrong information for code placement and other
optimizations.

Regards

Antoine.