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gh-146527: Heap-allocate gc_stats to avoid bloating PyInterpreterState#148057
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pablogsal merged 1 commit intoApr 4, 2026
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gh-146527: Heap-allocate gc_stats to avoid bloating PyInterpreterState#148057pablogsal merged 1 commit into
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…erState The gc_stats struct contains ring buffers of gc_generation_stats entries (11 young + 3×2 old on default builds). Embedding it inline in _gc_runtime_state, which is itself inline in PyInterpreterState, pushed fields like _gil.locked and threads.head to offsets beyond what out-of-process profilers and debuggers can reasonably read in a single buffer (e.g. offset 9384 for _gil.locked vs an 8 KiB read buffer). Heap-allocate generation_stats via PyMem_RawCalloc in _PyGC_Init and free it in _PyGC_Fini. This shrinks PyInterpreterState by ~1.6 KiB and keeps the GIL, thread-list, and other frequently-inspected fields at stable, low offsets.
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…erState (python#148057) The gc_stats struct contains ring buffers of gc_generation_stats entries (11 young + 3×2 old on default builds). Embedding it inline in _gc_runtime_state, which is itself inline in PyInterpreterState, pushed fields like _gil.locked and threads.head to offsets beyond what out-of-process profilers and debuggers can reasonably read in a single buffer (e.g. offset 9384 for _gil.locked vs an 8 KiB read buffer). Heap-allocate generation_stats via PyMem_RawCalloc in _PyGC_Init and free it in _PyGC_Fini. This shrinks PyInterpreterState by ~1.6 KiB and keeps the GIL, thread-list, and other frequently-inspected fields at stable, low offsets.
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This change introduced a memory leak: I wrote #150969 to fix it. The "free" part was only done in Python/gc_free_threading.c, not in Python/gc.c. |
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The gc_stats struct contains ring buffers of gc_generation_stats
entries (11 young + 3×2 old on default builds). Embedding it inline
in _gc_runtime_state, which is itself inline in PyInterpreterState,
pushed fields like _gil.locked and threads.head to offsets beyond
what out-of-process profilers and debuggers can reasonably read in
a single buffer (e.g. offset 9384 for _gil.locked vs an 8 KiB read
buffer).
Heap-allocate generation_stats via PyMem_RawCalloc in _PyGC_Init and
free it in _PyGC_Fini. This shrinks PyInterpreterState by ~1.6 KiB
and keeps the GIL, thread-list, and other frequently-inspected fields
at stable, low offsets.