GH-136410: Faster side exits #136411
GH-136410: Faster side exits #136411
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| // from being immediately detected as cold and invalidated. | ||
| cold->vm_data.warm = true; | ||
| if (_PyJIT_Compile(cold, cold->trace, 1)) { | ||
| Py_DECREF(cold); |
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It's immortal. Decrefing won't do anything. I think you mean to call the dealloc function on it?
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Good spot. I think I need to move making it immortal to after it is fully created.
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@pablogsal any ideas what this failure means? https://github.com/python/cpython/actions/runs/16140914160/job/45547999926?pr=136411 |
Is a race condition in the tests that will be fixed by #136347 |
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Performance is in the noise:
However, I wouldn't expect much of a speedup by reducing the size of exits, so this seems reasonable. |
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I think the benchmarking public mirror is down. Can you please share the link when it comes up again? |
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Note to self: The cold exit executor should be freed when freeing the interpreter to avoid leaking memory. |
This PR reinstates the
_COLD_EXITuop, but this time expects the exit to be passed, not the executor.This way we only need one jitted stub, not hundreds.
Using stubs hugely simplifies
_EXIT_TRACEas all it needs to do is jump to the exit's executor.The x86-64 stencil for
_EXIT_TRACEshrinks from 384 bytes to 36 bytes, although it does require one extra_CHECK_VALIDITY(19 bytes) to be added to each trace.Since traces often contain multiple
_EXIT_TRACEs this is a substantial space saving.