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gh-92914: Round the allocated size for lists up to the even number #92915

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merged 5 commits into from May 19, 2022
Merged

gh-92914: Round the allocated size for lists up to the even number #92915

merged 5 commits into from May 19, 2022

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serhiy-storchaka
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@serhiy-storchaka serhiy-storchaka commented May 18, 2022

Closes #92914.

@serhiy-storchaka serhiy-storchaka requested a review from methane May 18, 2022
methane
methane reviewed May 18, 2022
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Objects/listobject.c Outdated
@@ -94,6 +94,16 @@ list_preallocate_exact(PyListObject *self, Py_ssize_t size)
assert(self->ob_item == NULL);
assert(size > 0);

/* Since the Python memory allocator has granularity of 16 bytes,
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@methane methane May 18, 2022

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alignment is 8bytes on 32bit platform.

cpython/Objects/obmalloc.c

Lines 878 to 884 in b86d783

#if SIZEOF_VOID_P > 4
#define ALIGNMENT 16 /* must be 2^N */
#define ALIGNMENT_SHIFT 4
#else
#define ALIGNMENT 8 /* must be 2^N */
#define ALIGNMENT_SHIFT 3
#endif

So I think we don't need the else { block.

@serhiy-storchaka serhiy-storchaka changed the title gh-92914: Always round up the size allocated for lists up to 16 bytes gh-92914: Round up the allocated size for lists up to the even number May 18, 2022
@serhiy-storchaka serhiy-storchaka changed the title gh-92914: Round up the allocated size for lists up to the even number gh-92914: Round the allocated size for lists up to the even number May 18, 2022
@serhiy-storchaka serhiy-storchaka merged commit 8a6af5a into python:main May 19, 2022
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miss-islington commented May 19, 2022

Thanks @serhiy-storchaka for the PR 🌮🎉.. I'm working now to backport this PR to: 3.10, 3.11.
🐍🍒⛏🤖

@serhiy-storchaka serhiy-storchaka deleted the list-allocate-round-up branch May 19, 2022
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bedevere-bot commented May 19, 2022

GH-92941 is a backport of this pull request to the 3.11 branch.

miss-islington pushed a commit to miss-islington/cpython that referenced this pull request May 19, 2022
@serhiy-storchaka @miss-islington
pythongh-92914: Round the allocated size for lists up to the even num…
7514c35 
…ber (pythonGH-92915)

(cherry picked from commit 8a6af5a)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
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bedevere-bot commented May 19, 2022

GH-92942 is a backport of this pull request to the 3.10 branch.

miss-islington pushed a commit to miss-islington/cpython that referenced this pull request May 19, 2022
@serhiy-storchaka @miss-islington
pythongh-92914: Round the allocated size for lists up to the even num…
6a1738a 
…ber (pythonGH-92915)

(cherry picked from commit 8a6af5a)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
ambv pushed a commit that referenced this pull request Jun 7, 2022
@miss-islington @serhiy-storchaka
gh-92914: Round the allocated size for lists up to the even number (G…
9204364 
…H-92915) (GH-92942)

(cherry picked from commit 8a6af5a)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
miss-islington added a commit that referenced this pull request Jun 14, 2022
@miss-islington @serhiy-storchaka
gh-92914: Round the allocated size for lists up to the even number (G…
73c8f3f 
…H-92915)

(cherry picked from commit 8a6af5a)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
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Add padding in list allocation
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