Major python performance degradation with Windows 11 22H2

After upgrading to WIndows 11 22H2, I noted a significant performance degradation running python programs in the Anaconda PowerShell. For example, a cpu bound program which normally took about 50 seconds to run now takes about 90 seconds. I’d also noticed that conda update and the like seem to run much slower as well, although I haven’t specifically measured.

The problem seems to be specific to the Intel Alder Lake (and probably Raptor Lake) processor families. With Win 22H1, the python programs in the Anaconda PowerShell were assigned to the performance cores. Under 22H2, they now seem to be allocated to the efficiency cores, resulting in the performance hit. (I observed the core utilizations using Resource Monitor and XTU). Disabling the e-cores in bios would would return the better level of performance, validating the other observations.

I’ve seen nothing about this in any of the Microsoft documentation, although there are reports of incorrect assignment of cores for other programs.

This has been verified on two different machines in my environment…one a 12900K and the other a 12700K.

Posted as a caution to others upgrading to 22H2 (I’ve since downgraded). Would also be curious whether others have observed the same issues.