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gh-136157: Optimize asyncio.to_thread to avoid contextvars.copy_context() overhead for empty contexts #136159

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gh-136157: Optimize asyncio.to_thread to avoid contextvars.copy_context() overhead for empty contexts #136159

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@heliang666s heliang666s commented Jul 1, 2025 •
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bedevere-app bot commented Jul 1, 2025

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@heliang666s heliang666s changed the title gh136157:Optimize asyncio.to_thread to avoid contextvars.copy_context() overhead for empty contexts gh-136157:Optimize asyncio.to_thread to avoid contextvars.copy_context() overhead for empty contexts Jul 1, 2025
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bedevere-app bot commented Jul 1, 2025

Most changes to Python require a NEWS entry. Add one using the blurb_it web app or the blurb command-line tool.

If this change has little impact on Python users, wait for a maintainer to apply the skip news label instead.

@picnixz picnixz changed the title gh-136157:Optimize asyncio.to_thread to avoid contextvars.copy_context() overhead for empty contexts gh-136157: Optimize asyncio.to_thread to avoid contextvars.copy_context() overhead for empty contexts Jul 1, 2025
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ZeroIntensity reviewed Jul 1, 2025
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Please provide some benchmarks.

Lib/asyncio/threads.py
Comment on lines +24 to +27
if not ctx:
callback = functools.partial(func, *args, **kwargs)
else:
callback = functools.partial(ctx.run, func, *args, **kwargs)
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Hm, couldn't we alternatively add a fast path to Context.run?

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I don't think so. Please see the issue for details.

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Please provide some benchmarks.

Ah, oops, didn't look at the issue. It would be helpful to put them in the PR description as well.

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