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bpo-46841: Improve the failure stats for COMPARE_OP#31663

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brandtbucher merged 2 commits into
python:mainfrom
brandtbucher:more-compare-op-stats
Mar 3, 2022
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bpo-46841: Improve the failure stats for COMPARE_OP#31663
brandtbucher merged 2 commits into
python:mainfrom
brandtbucher:more-compare-op-stats

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@brandtbucher

@brandtbucher brandtbucher commented Mar 3, 2022 •
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With the move to inline caching, jumps are getting a bit longer. This adds new category of COMPARE_OP failures for the (increasingly more common) case where a COMPARE_OP instruction is followed by an EXTENDED_ARG.

New stats for a full pyperformance run:

Kind Count Ratio
unquickened 7348739 0.4%
specialization.deferred 359371048 21.7%
specialization.deopt 15730 0.0%
hit 1289210975 77.8%
miss 943057 0.1%

Specialization attempts

Count Ratio
Success 289083 4.8%
Failure 5723386 95.2%
Failure kind Count Ratio
extended arg 2473174 43.2%
not followed by cond jump 1258612 22.0%
float long 671682 11.7%
set 579241 10.1%
different types 165539 2.9%
bool 137038 2.4%
tuple 119632 2.1%
other 115566 2.0%
big int 95547 1.7%
bytes 46481 0.8%
baseobject 37335 0.7%
list 22634 0.4%
string 704 0.0%
long float 201 0.0%

https://bugs.python.org/issue46841

sweeneyde
sweeneyde approved these changes Mar 3, 2022
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@sweeneyde sweeneyde left a comment •
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Looks good.

We could also consider packing extended opargs into the top 13 bits of cache->mask when it fits there.

Edit: I suppose it would be difficult to do next_instr++ the correct number of times in ceval. Store how far to jump ahead for that branch as well?

@brandtbucher brandtbucher mentioned this pull request Mar 3, 2022
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@brandtbucher

brandtbucher commented Mar 3, 2022

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@markshannon is already brainstorming ideas for how to tackle the general problem of longer jumps in faster-cpython/ideas#297 and faster-cpython/ideas#301. We should probably wait to see how that pans out first before adding a bunch of new logic to the different COMPARE_OP specializations.

@brandtbucher brandtbucher merged commit 127797f into python:main Mar 3, 2022
@markshannon

markshannon commented Mar 3, 2022

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Feel free to add suggestions to faster-cpython/ideas#301.

faster-cpython/ideas#297 is more about giving the bytecode compiler freedom to lay out basic blocks.

@brandtbucher brandtbucher mentioned this pull request Apr 10, 2022
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@brandtbucher brandtbucher deleted the more-compare-op-stats branch July 21, 2022 19:53
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