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[3.13] GH-133136: Revise QSBR to reduce excess memory held (gh-135473) - #136480
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…35473) The free threading build uses QSBR to delay the freeing of dictionary keys and list arrays when the objects are accessed by multiple threads in order to allow concurrent reads to proceed with holding the object lock. The requests are processed in batches to reduce execution overhead, but for large memory blocks this can lead to excess memory usage. Take into account the size of the memory block when deciding when to process QSBR requests. Also track the amount of memory being held by QSBR for mimalloc pages. Advance the write sequence if this memory exceeds a limit. Advancing the sequence will allow it to be freed more quickly. Process the held QSBR items from the "eval breaker", rather than from `_PyMem_FreeDelayed()`. This gives a higher chance that the global read sequence has advanced enough so that items can be freed. (cherry picked from commit 113de85) Co-authored-by: Neil Schemenauer <nas-github@arctrix.com> Co-authored-by: Sam Gross <colesbury@gmail.com>
This was referenced Jul 9, 2025
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nascheme
marked this pull request as ready for review
July 9, 2025 20:51
nascheme
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July 9, 2025 20:51
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Yhg1s
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Jul 29, 2025
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The free threading build uses QSBR to delay the freeing of dictionary keys and list arrays when the objects are accessed by multiple threads in order to allow concurrent reads to proceed with holding the object lock. The requests are processed in batches to reduce execution overhead, but for large memory blocks this can lead to excess memory usage.
Take into account the size of the memory block when deciding when to process QSBR requests.
Also track the amount of memory being held by QSBR for mimalloc pages. Advance the write sequence if this memory exceeds a limit. Advancing the sequence will allow it to be freed more quickly.
Process the held QSBR items from the "eval breaker", rather than from
_PyMem_FreeDelayed(). This gives a higher chance that the global read sequence has advanced enough so that items can be freed.(cherry picked from commit 113de85)
Co-authored-by: Sam Gross colesbury@gmail.com