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bpo-40521: Remove freelist from collections.deque() by rhettinger · Pull Request #21073 · python/cpython · GitHub
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bpo-40521: Remove freelist from collections.deque()#21073

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rhettinger merged 1 commit into
python:masterfrom
rhettinger:deque_freelist
Jun 23, 2020
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bpo-40521: Remove freelist from collections.deque()#21073
rhettinger merged 1 commit into
python:masterfrom
rhettinger:deque_freelist

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rhettinger commented Jun 23, 2020 •
edited by bedevere-bot
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vstinner approved these changes Jun 23, 2020
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Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality Hide comment

LGTM.

But I'm curious, why removing it? The free list is not longer faster than always calling PyMem_Malloc/PyMem_Free?

Previously, PyMem_Malloc/PyMem_Free called libc malloc/free. But now it's the pymalloc memory allocator which is faster than libc allocator for small memory allocation (up to 512 bytes). Maybe pymalloc made the free list less interesting?

rhettinger commented Jun 23, 2020

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Deques only call the allocator once every 64 updates, so the average cost is small.

rhettinger merged commit 32f2eda into python:master Jun 23, 2020
fasih pushed a commit to fasih/cpython that referenced this pull request Jun 29, 2020
bpo-40521: Remove freelist from collections.deque() (pythonGH-21073)
2a1fe84
rhettinger added a commit to rhettinger/cpython that referenced this pull request Mar 20, 2021
Revert "bpo-40521: Remove freelist from collections.deque() (pythonGH… …
39ebce3
…-21073)" This reverts commit 32f2eda. It can be re-applied if the subinterpreter PEP is approved. Otherwise, the commit degraded performance with no offsetting benefit.
rhettinger added a commit that referenced this pull request Mar 25, 2021
Revert "bpo-40521: Remove freelist from collections.deque() (GH-21073)… …
3bb1987
…" (GH-24944) This reverts commit 32f2eda. It can be re-applied if the subinterpreter PEP is approved. Otherwise, the commit degraded performance with no offsetting benefit.
vstinner mentioned this pull request Apr 10, 2022
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