b"".join should release GIL in case of memoryview
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Description
Bug report
Bug description:
CPython PR #17757 allowed the GIL to be released during b"".join() operations. However, this optimization currently only triggers if every passed object is of type bytes; it falls back to acquiring the GIL if it encounters mutable buffers. While reacquiring the GIL is necessary for mutable types like bytearray, we can still safely drop the GIL for memoryview objects that expose immutable bytes.
Please refer to https://github.com/fsspec/gcsfs/pull/795#discussion_r3032749881 for more context.
cc: @martindurant
CPython versions tested on:
CPython main branch
Operating systems tested on:
Linux
Linked PRs
- gh-148456
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by reviewing CPython PR #17757 and the linked PR gh-148456, then trace the b"".join handling for memoryview objects. Done means immutable-byte memoryviews can use the GIL-releasing path while mutable buffers still reacquire the GIL, with the relevant behavior covered by tests.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- performance
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100