Hello all, Over in Ubuntu, we've gotten reports about some performance regressions in Python 2.7 when moving from Trusty (14.04 LTS) to Xenial (16.04 LTS). Trusty's version is based on 2.7.6 while Xenial's version is based on 2.7.12 with bits of .13 cherry picked. We've not been able to identify any change in Python itself (or the Debian/Ubuntu deltas) which could account for this, so the investigation has led to various gcc compiler options and version differences. In particular disabling LTO (link-time optimization) seems to have a positive impact, but doesn't completely regain the loss. 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_scmTRDmVauBprKL8ei... The document should be public for comments and editing. If you have any thoughts, or other lines of investigation you think are worthwhile pursuing, please add your comments to the document. Cheers, -Barry