Description

savannahostrowski

opened on Sep 17, 2025

Issue body actions

Following a conversation at the CPython Core Dev Sprint, this is an uber issue tracking JIT performance goals and planning for 3.15 and 3.16.

The goal here is to capture our goals and the work that we believe is necessary to enable the JIT (on by default).

3.15 (May 2026)

Goals & "features"

Must Haves

• 5% faster (geometric mean)
  • Best case: 50% faster
  • Worst case: -10% faster
• JIT coverage (i.e., how much code is being JIT'ted): 80% JIT coverage can be improved considerably #142982
• Free-threading supported (pre-beta) Make the JIT thread-safe #133171 gh-141594: A free-threaded JIT (Part 1) #141595
• Support for out-of-process profilers and debuggers Supporting stack unwinding in the JIT compiler #126910

Nice to haves

• 10% faster (geometric mean)
  • Best case: 100% faster
  • Worst case 1% slower
• JIT coverage (i.e., how much code is being JIT'ted): 90%
• Robust documentation

How will we do this?

• Register allocation GH-135379: Top of stack caching for the JIT. #135465
• More optimizations Better uop coverage in the JIT optimizer #131798 Eliminate redundant refcounting in the JIT #134584
• Trace recording Trace recording JIT #139109
• Code gen
• LLVM 21 Update JIT builds to use LLVM 21 #140479
• Warm up faster
• More specialization Broader specialization in the Specializing Adaptive Interpreter for better JIT performance #143732

3.16

Goals & "features"

Must Haves

• ~ similar debuggability and performance across Tier 1 platforms
• 2+ maintainers in front-end, middle-end, and back-end
• ...Anything listed in 3.15 nice to have that was not achieved (e.g. docs, better coverage, faster)

How will we do this?

• Unboxing (int/float/other types)
• LLVM 22

Linked PRs

• gh-139038: Add JIT What's New for 3.15 #142845
• gh-139038: Add macOS performance numbers for the JIT #143479
• gh-139038: Update JIT perf figures for 3.14a4 #143705
• gh-139038: Link to Savannah's webpage for JIT results #146013
• gh-139038: Update JIT results in preparation for 3.15a8 #148018
• gh-139038: Credit more people for JIT in 3.15 #148359
• gh-139038: Add whatsnew entry for jit unique reference tracking #148572
• gh-139038: Update final JIT figures for 3.15b1 #149210

Reacted by Rafał Pitoń, Wulian233, An Long, Nadeshiko Manju, Lukas Heumos, Furkan Onder, porly1985, Sergio Castillo, Aleksandr Andreev, ResponsibleMove and 17 more

Activity

1. savannahostrowski

   assigned

   Fidget-Spinner

   ,

   brandtbucher

   ,

   markshannon

   and

   savannahostrowski

   on Sep 17, 2025
2. savannahostrowski

   added

   topic-JIT

   on Sep 17, 2025
3. picnixz

   added

   interpreter-core(Objects, Python, Grammar, and Parser dirs)(Objects, Python, Grammar, and Parser dirs)

   on Sep 17, 2025
4. corona10 commented on Sep 18, 2025

   

   corona10

   on Sep 18, 2025

   Member

   More actions

   Here is link the issue related JITxFree-threadng: #133171

   Reacted by Savannah Ostrowski
5. hugovk

   added a commit that references this issue on Dec 17, 2025

   gh-139038: Add JIT What's New for 3.15 (#142845)

   1fc3039
6. Fidget-Spinner

   added 2 commits that reference this issue on Jan 6, 2026

   gh-139038: Add macOS performance numbers for the JIT (GH-143479)

   d9c1235

   gh-139038: Update JIT perf figures for 3.14a4 (GH-143705)

   9633f95
7. diegorusso

   self-assigned this

   on Jan 12, 2026
8. reidenong

   added a commit that references this issue on Jan 12, 2026

   pythongh-139038: Update JIT perf figures for 3.14a4 (pythonGH-143705)

   7b29565
9. thunder-coding

   added 2 commits that reference this issue on Feb 15, 2026

   pythongh-139038: Add macOS performance numbers for the JIT (pythonGH-…

   0aec9b3

   pythongh-139038: Update JIT perf figures for 3.14a4 (pythonGH-143705)

   9d06f54
10. hugovk

    added a commit that references this issue on Mar 16, 2026

    gh-139038: Link to Savannah's webpage for JIT results (#146013)

    e2e6203
11. Fidget-Spinner

    added a commit that references this issue on Apr 2, 2026

    gh-139038: Update JIT results in preparation for 3.15a8 (GH-148018)

    74a82a2
12. Fidget-Spinner

    added 2 commits that reference this issue on Apr 10, 2026

    gh-139038: Credit more people for JIT in 3.15 (GH-148359)

    c4d9512

    gh-139038: Add whatsnew entry for jit unique reference tracking (GH-1…

    aee63e2
13. ljfp

    added 4 commits that reference this issue on Apr 25, 2026

    pythongh-139038: Link to Savannah's webpage for JIT results (python#1…

    37e9dc4

    pythongh-139038: Update JIT results in preparation for 3.15a8 (python…

    a03e15b

    pythongh-139038: Credit more people for JIT in 3.15 (pythonGH-148359)

    ca8437c

    pythongh-139038: Add whatsnew entry for jit unique reference tracking (…

    c64e2f1
14. hugovk

    added a commit that references this issue on May 1, 2026

    gh-139038: Update final JIT figures for 3.15rc1 (#149210)

    fa54244

Issue actions