perf: Release GIL during cancellation check

[kthui]

What does the PR do?

Release the GIL while checking for cancellation. Another Python thread can be performing useful work while the cancellation status is being checked.

Checklist

• PR title reflects the change and is of format <commit_type>: <Title>
• Changes are described in the pull request.
• Related issues are referenced.
• Populated github labels field
• Added test plan and verified test passes.
• Verified that the PR passes existing CI.
• Verified copyright is correct on all changed files.
• Added succinct git squash message before merging ref.
• All template sections are filled out.
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Commit Type:

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• build
• ci
• docs
• feat
• fix
• perf
• refactor
• revert
• style
• test

Related PRs:

triton-inference-server/vllm_backend#54

Where should the reviewer start?

Can start by verifying the cancellation function, where the GIL is released during its execution, does not access any Python objects.

Test plan:

This is a performance improvement, so any issue should be covered by existing test cases.

• CI Pipeline ID: 17061062

Caveats:

N/A

Background

Need to improve the performance on vLLM backend.

Related Issues: (use one of the action keywords Closes / Fixes / Resolves / Relates to)

N/A

[oandreeva-nv]

LGTM!