perf(profiling): reuse asyncio task unwind buffers

[taegyunkim]

Description

Reuse native stack-collector buffers while unwinding asyncio Tasks. This mirrors the greenlet buffer-reuse optimization by keeping per-thread StackInfo slots and per-task coroutine FrameStack buffers alive across samples, reducing allocator churn and native heap growth in asyncio services with many long-lived tasks.

Testing

• scripts/lint style tests/profiling/collector/test_asyncio_buffer_reuse.py && scripts/lint cformat && scripts/lint spelling releasenotes/notes/perf-profiling-unwind-asyncio-tasks-buffer-reuse-4f6e2a8b9c1d0e3f.yaml
• scripts/run-tests --venv 95f8b96 tests/profiling/collector/test_asyncio_buffer_reuse.py -- -- tests/profiling/collector/test_asyncio_buffer_reuse.py -k test_asyncio_unwind_tasks_rss_stable
• scripts/run-tests --venv 95f8b96 tests/profiling/collector/test_stack_asyncio_basic.py -- -- tests/profiling/collector/test_stack_asyncio_basic.py -k test_asyncio_basic

Risks

Low. The change preserves existing stack-rendering behavior while reusing cleared buffers between samples. Potential risk is stale task stack reuse; mitigated by resetting active counts at unwind entry and erasing coroutine-stack entries for tasks that are no longer present.

Additional Notes

Release note included.

[cit-pr-commenter-54b7da]

Codeowners resolved as

ddtrace/internal/datadog/profiling/stack/echion/echion/threads.h        @DataDog/profiling-python
ddtrace/internal/datadog/profiling/stack/src/echion/threads.cc          @DataDog/profiling-python
releasenotes/notes/perf-profiling-unwind-asyncio-tasks-buffer-reuse-4f6e2a8b9c1d0e3f.yaml  @DataDog/apm-python
tests/profiling/collector/test_asyncio_buffer_reuse.py                  @DataDog/profiling-python

[datadog-datadog-prod-us1-2]

 

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