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Too many specialization attempts when we are never going to succeed. #93354

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markshannon opened this issue May 30, 2022 · 0 comments
Closed

Too many specialization attempts when we are never going to succeed. #93354

markshannon opened this issue May 30, 2022 · 0 comments
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3.11 only security fixes 3.12 only security fixes performance Performance or resource usage type-bug An unexpected behavior, bug, or error

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@markshannon
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There are quite a few (value, operation) pairs that we cannot specialize.
For those operations, we can spend a significant amount of time repeatedly attempting to specialize, and repeatedly failing.

There is a well known fix for this, which is "exponential backoff".
The idea is that each time you fail to specialize (or otherwise fail to optimize) the countdown counter is set to twice its previous starting value.
Currently, we attempt to specialize every 64 executions, with exponential backoff we would start at 31, then 63, then 127 until we reach a limit of 4095 for a 12 bit counter and 4 bit backoff exponent.

See faster-cpython/ideas#397 for more details
@markshannon markshannon added the type-bug An unexpected behavior, bug, or error label May 30, 2022
@AA-Turner AA-Turner added performance Performance or resource usage 3.12 only security fixes labels May 30, 2022
markshannon added a commit that referenced this issue May 31, 2022
@markshannon
GH-93354: Use exponential backoff to avoid excessive specialization a…
eb618d5 
…ttempts. (GH-93355)
@markshannon markshannon added the 3.11 only security fixes label May 31, 2022
markshannon added a commit that referenced this issue May 31, 2022
@markshannon
[3.11] GH-93354: Use exponential backoff to avoid excessive specializ…
852dca8 
…ation attempts. (GH-93355)

(cherry picked from commit eb618d5)

Co-authored-by: Mark Shannon <mark@hotpy.org>
@Fidget-Spinner Fidget-Spinner mentioned this issue Jun 15, 2022
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@bedevere-bot bedevere-bot mentioned this issue Jun 26, 2022
Merged
ambv added a commit that referenced this issue Jun 30, 2022
@markshannon @ambv
[3.11] GH-93354: Use exponential backoff to avoid excessive specializ…
113b309 
…ation attempts (GH-93355) (GH-93379)

Co-authored-by: Mark Shannon <mark@hotpy.org>
Co-authored-by: Łukasz Langa <lukasz@langa.pl>
@bedevere-bot bedevere-bot mentioned this issue Oct 7, 2022
Merged
brandtbucher added a commit that referenced this issue Oct 12, 2022
@brandtbucher
[3.11] GH-93354: Fix PRECALL's adaptive backoff (GH-98011)
0a67f82
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