[subinterpreters] Make free lists and unicode caches per-interpreter

[vstinner]

BPO	40521
Nosy	@rhettinger, @mdickinson, @vstinner, @markshannon, @corona10, @shihai1991, @JunyiXie
PRs	bpo-40521: Disable Unicode caches in isolated subinterpreters #19933 bpo-40521: Disable free lists in subinterpreters #19937 bpo-40521: Disable list free list in subinterpreters #19959 bpo-40521: Disable method cache in subinterpreters #19960 bpo-40521: Add PyInterpreterState.unicode #20081 bpo-40521: Add PyInterpreterState.unicode #20082 bpo-40521: Per-interpreter interned strings #20085 bpo-40521: Fix update_slot() whne INTERN_NAME_STRINGS is not defined #20246 bpo-40521: Make tuple free list per-interpreter #20247 bpo-40521: Make float free list per-interpreter #20636 bpo-40521: Make slice cache per-interpreter #20637 bpo-40521: Make frame free list per-interpreter #20638 bpo-40521: Make list free list per-interpreter #20642 bpo-40521: Make async gen free lists per-interpreter #20643 bpo-40521: Make context free list per-interpreter #20644 bpo-40521: Make dict free lists per-interpreter #20645 bpo-40521: Make the empty frozenset per interpreter #21068 bpo-40521: Remove freelist from collections.deque() #21073 bpo-40521: Make bytes singletons per interpreter #21074 bpo-40521: Cleanup code of free lists #21082 bpo-40521: Empty frozenset is no longer a singleton #21085 bpo-40521: Make MemoryError free list per interpreter #21086 bpo-40521: Make empty Unicode string per interpreter #21096 bpo-40521: Optimize PyUnicode_New(0, maxchar) #21099 bpo-40521: Make Unicode latin1 singletons per interpreter #21101 bpo-40521: Fix _PyContext_Fini() #21103 bpo-40521: Always create the empty tuple singleton #21116 bpo-40521: Optimize PyBytes_FromStringAndSize(str, 0) #21142 bpo-40521: Cleanup finalize_interp_types() #21265 bpo-40521: Fix PyUnicode_InternInPlace() #22376 bpo-40521: [subinterpreters] Make dtoa bigint free list per-interpreter #24821 Revert "bpo-40521: Remove freelist from collections.deque() (GH-21073)" #24944 Revert "bpo-40521: [subinterpreters] Make dtoa bigint free list per-interpreter" #24964 bpo-40521: Convert deque freelist from global vars to instance vars #25906 bpo-46006: Revert "bpo-40521: Per-interpreter interned strings (GH-20085)" #30422 [3.10] bpo-46006: Revert "bpo-40521: Per-interpreter interned strings (GH-20085)" (GH-30422) #30425 [3.10] bpo-46006: Revert "bpo-40521: Per-interpreter interned strings (GH-20085)" (GH-30422) #30433
Files	bench_tuple.patch microbench_tuple.py bench_dict.patch interned_bug.py bench_dtoa.py

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2020-05-05.15:48:02.489>
labels = ['expert-subinterpreters', '3.10']
title = '[subinterpreters] Make free lists and unicode caches per-interpreter'
updated_at = <Date 2022-01-06.15:24:07.868>
user = 'https://github.com/vstinner'

bugs.python.org fields:

activity = <Date 2022-01-06.15:24:07.868>
actor = 'vstinner'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Subinterpreters']
creation = <Date 2020-05-05.15:48:02.489>
creator = 'vstinner'
dependencies = []
files = ['49212', '49213', '49216', '49699', '49899']
hgrepos = []
issue_num = 40521
keywords = ['patch']
message_count = 56.0
messages = ['368175', '368177', '368187', '368278', '368283', '368807', '368808', '369407', '370636', '370733', '370734', '370735', '370737', '370740', '370741', '370742', '370754', '370755', '370756', '370757', '370771', '370928', '370969', '372146', '372148', '372161', '372168', '372169', '372176', '372181', '372207', '372209', '372216', '372220', '372223', '372250', '372357', '372795', '377368', '383789', '383790', '383829', '385950', '388492', '388493', '388617', '389226', '389294', '389305', '389525', '389527', '393787', '395860', '409819', '409856', '409862']
nosy_count = 7.0
nosy_names = ['rhettinger', 'mark.dickinson', 'vstinner', 'Mark.Shannon', 'corona10', 'shihai1991', 'JunyiXie']
pr_nums = ['19933', '19937', '19959', '19960', '20081', '20082', '20085', '20246', '20247', '20636', '20637', '20638', '20642', '20643', '20644', '20645', '21068', '21073', '21074', '21082', '21085', '21086', '21096', '21099', '21101', '21103', '21116', '21142', '21265', '22376', '24821', '24944', '24964', '25906', '30422', '30425', '30433']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue40521'
versions = ['Python 3.10']

[vstinner]

tuple, dict and frame use free lists to optimize the creation of objects.

Unicode uses "interned" strings to reduce the Python memory footprint and speedup dictionary lookups.

Unicode also uses singletons for single letter Latin1 characters ([U+0000; U+00FF] range).

All these optimizations are incompatible with isolated subinterpreters, since caches are currently shared by all inteprepreters. These caches should be made per-intepreter. See bpo-40512 "Meta issue: per-interpreter GIL" for the rationale.

I already made small integer singletons per interpreter in bpo-38858:

• commit 5dcc06f
• commit 630c8df.

[vstinner]

New changeset 607b102 by Victor Stinner in branch 'master':
bpo-40521: Disable Unicode caches in isolated subinterpreters (GH-19933)
607b102

[vstinner]

New changeset b4b5386 by Victor Stinner in branch 'master':
bpo-40521: Disable free lists in subinterpreters (GH-19937)
b4b5386

[vstinner]

New changeset 89fc4a3 by Victor Stinner in branch 'master':
bpo-40521: Disable method cache in subinterpreters (GH-19960)
89fc4a3

[vstinner]

New changeset b7aa23d by Victor Stinner in branch 'master':
bpo-40521: Disable list free list in subinterpreters (GH-19959)
b7aa23d

[vstinner]

I wrote a draft PR to make interned strings per-interpreter. It does crash because it requires to make method cache and _PyUnicode_FromId() (bpo-39465) compatible with subinterpreters.

[vstinner]

New changeset 3d17c04 by Victor Stinner in branch 'master':
bpo-40521: Add PyInterpreterState.unicode (GH-20081)
3d17c04