Please enable PGO and LTO for arm64

[Ali Saidi]

The rules file conditionally enables PGO and LTO in the python3 build and while it's enabled for many platforms it's not enabled for arm64. This is worth about 30% performance. Please enable it.

A patch is available here with the original debian bug report:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=934812

[Dan Streetman (ddstreet)]

> This is worth about 30% performance.

can you share some performance tests used to measure this improvement?

[Ali Saidi (alisaidi)]

Some of the subcomponents of the pyperformance suite:
https://github.com/python/pyperformance/tree/master/pyperformance/benchmarks

[Dan Streetman (ddstreet)]

I've been told that this is planned for the 3.7.5 release of python3.7 in 18.04. The release schedule for that is here:
https://www.python.org/dev/peps/pep-0537/#id4

[Dan Streetman (ddstreet)]

To clarify, that's the release schedule for python 3.7.5.

The pgo/lto change for arm64 is already in the 19.10 Ubuntu release of python3 (3.7.4), so once the 3.7.5 version is released upstream, then Debian will update to it, then Ubuntu 19.10 (or 20.04) will update to it, then it will be backported to 18.04.

[Brian Murray (brian-murray)]

python3-defaults (3.7.5-1) unstable; urgency=medium

  * Bump version to 3.7.5.
  * Bump standards version.

 -- Matthias Klose <email address hidden> Wed, 02 Oct 2019 14:31:29 +0200

[Brian Murray (brian-murray)]

This is actually being tracked in bug 1835738.