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GeezerVison is showing github.com — bpo-37029: keep usable_arenas in sorted order without searching by tim-one · Pull Request #13612 · python/cpython

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@tim-one

@tim-one tim-one commented May 28, 2019 •
edited by bedevere-bot
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This adds a vector of "search fingers" so that usable_arenas can be kept in sorted order (by number of free pools) via constant-time operations instead of linear search.

This should reduce worst-case time for reclaiming a great many objects from O(A**2) to O(A), where A is the number of arenas.

https://bugs.python.org/issue37029

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@tim-one
Issue 37029: first stab at removing all searching to keep usable_arenas
c691a69 
sorted by number of free pools.
@the-knights-who-say-ni the-knights-who-say-ni added the CLA signed label May 28, 2019
@bedevere-bot bedevere-bot added the awaiting core review label May 28, 2019
@tim-one tim-one self-assigned this May 28, 2019
blurb-it Bot and others added 4 commits May 28, 2019 17:02
@blurb-it
📜🤖 Added by blurb_it.
f4a60e8
@tim-one
Beefed up an assert; added the BPO number to a comment.
efe1e63
@tim-one
Merge branch 'remove-arena-search' of https://github.com/tim-one/cpython
0b36d42 
 into remove-arena-search
@tim-one
And added one more assert.
0463a7d
methane
methane reviewed May 29, 2019
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Comment thread Objects/obmalloc.c Resolved

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methane
methane approved these changes May 31, 2019
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@bedevere-bot bedevere-bot added awaiting merge and removed awaiting core review labels May 31, 2019
pitrou
pitrou reviewed May 31, 2019
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@pitrou pitrou left a comment

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Looks neat, just a comment.

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Comment thread Objects/obmalloc.c
@@ -1172,6 +1189,9 @@ static struct arena_object* unused_arena_objects = NULL;
*/

@pitrou pitrou May 31, 2019

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Add comment documenting that they are sorted in number of free pools?

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@tim-one tim-one May 31, 2019

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I'd rather not, unless you feel strongly about it. This has been documented all along, but up where the main explanation of arenas lives (look at the comment block about usable_arenas at line 1150).

There are a bunch of moving parts here, and the style of the file is to give long-ish English explanations in uninterrupted comment blocks, with only the briefest of memory-jogging comments on declaration lines.

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@tim-one
tim-one merged commit 1c263e3 into python:master Jun 1, 2019
@bedevere-bot

bedevere-bot commented Jun 1, 2019

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@tim-one: Please replace # with GH- in the commit message next time. Thanks!
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@bedevere-bot bedevere-bot removed the awaiting merge label Jun 1, 2019
@tim-one
tim-one deleted the remove-arena-search branch June 1, 2019 02:30
DinoV pushed a commit to DinoV/cpython that referenced this pull request Jan 14, 2020
@tim-one @DinoV
bpo-37029: keep usable_arenas in sorted order without searching (pyth…
239f688 
…on#13612)

This adds a vector of "search fingers" so that usable_arenas can be kept in sorted order (by number of free pools) via constant-time operations instead of linear search.

This should reduce worst-case time for reclaiming a great many objects from O(A**2) to O(A), where A is the number of arenas.  See bpo-37029.
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@pitrou pitrou pitrou left review comments
@methane methane methane approved these changes

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5 participants

@tim-one @bedevere-bot @methane @pitrou @the-knights-who-say-ni
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