[New-bugs-announce] [issue23601] use small object allocator for dict key storage

[Julian Taylor]

New submission from Julian Taylor:

dictionary creation spends a not insignificant amount of time in malloc allocating keys objects. Python has a nice small object allocator that avoids a lot of this overhead and falls back to malloc for larger allocations.
Is there a reason the dictionary does not use that allocator for its keys objects?
doing so e.g. via attached incomplete patch improves small dict creation performance by 15%.

import  timeit
print(timeit.repeat("dict(a=5, b=2)"))

with change:
[0.42825599999923725, 0.4272580000015296, 0.4362329999985377]
without
[0.5160610000002634, 0.5181720000000496, 0.518421999999191]


or is there something I am overlooking and the use of PyMem_Malloc instead of PyObject_Malloc is an intentional design decision?

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components: Interpreter Core
files: 0001-use-small-object-allocator-for-keys-object.patch
keywords: patch
messages: 237439
nosy: jtaylor
priority: normal
severity: normal
status: open
title: use small object allocator for dict key storage
versions: Python 3.5
Added file: http://bugs.python.org/file38371/0001-use-small-object-allocator-for-keys-object.patch

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue23601>
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