[New-bugs-announce] [issue43889] Pickle performance regression in 3.10

Ken Jin report at bugs.python.org
Mon Apr 19 11:12:15 EDT 2021

New submission from Ken Jin <kenjin4096 at gmail.com>:

Hi everyone, I noticed on speed.python.org that the pickle benchmarks are noticeably slower:

Overall, pickle slowed down by >10%

Pickling list and dict is also slower by >10%:


For some reason, the pickle_pure_python benchmark which doesn't use the _pickle C library has no change.

The regression happened somewhere between commit 11159d2c9d6616497ef4cc62953a5c3cc8454afb and 3fc65b97d09fd29272fdf60d2e567bfb070da824. I don't know which commit caused it as there doesn't seem to be a change to _pickle.c. I have a weak hunch that it may be linked to Issue38530 (since the other commits in that time range are docs, sqllite3, ssl and unrelated python libraries) but I'm unsure. I'll try to bisect things this weekend if nobody's started on it by then.

Thanks for your time!

components: Library (Lib)
messages: 391380
nosy: alexandre.vassalotti, kj, pablogsal, serhiy.storchaka, vstinner
priority: normal
severity: normal
status: open
title: Pickle performance regression in 3.10
versions: Python 3.10

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