dask pyperformance benchmark hangs on win32 about cpython

[vstinner]

benchmark hangs

Do you mean that it uses all the CPU, or that the process hangs and do nothing?

Can you check which lines are executed when it "hangs"?

[vstinner]

I reproduced the issue. The problem comes from _WindowsTime of distributed/metrics.py.

Combine time.time() or time.monotonic() with time.perf_counter() to get an absolute clock with fine resolution.

https://github.com/dask/distributed/blob/d5edb4e536c9acc4998f803aacc0dd0188af21ce/distributed/metrics.py#L45-L98

[vstinner]

I reported the issue to the dask/distributed project and I proposed a fix:

• dask/distributed#8641
• dask/distributed#8642

[vstinner]

@mdboom: I suggest to close this issue since it's not a bug in Python, and it's now tracked in dask/distributed.

[mdboom]

I want to bring a discussion elsewhere back here.

@vstinner: I definitely have no experience with these Windows APIs, however, it seems that the change in 1d95451 introduced some stateful interaction between time.time and time.perf_counter, since they both now call py_win_perf_counter_frequency with the same global variable as base. Is this a regression for any code that calls time.time and time.perf_counter interleaved? What are the implications of that?

At a minimum, I think we should improve the "What's new" entry about this so people are aware of the interaction.

[vstinner]

the change in 1d95451 introduced some stateful interaction between time.time and time.perf_counter, since they both now call py_win_perf_counter_frequency with the same global variable as base.

• time.time() now calls GetSystemTimePreciseAsFileTime()
• time.perf_counter() is unchanged
• time.monotonic() now calls GetSystemTimePreciseAsFileTime().

It's documented at: https://docs.python.org/dev/whatsnew/3.13.html#time

[mdboom]

Yes, but why did that break dask? Because the assumption about time.time having low resolution no longer holds? I think the concern is for possibly breaking other libraries using these APIs.

Sorry, I see you answered my question elsewhere.