[Bug 254040] AMD 5950X hyperthreading strange performance swings

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=254040

Mark Johnston <markj@FreeBSD.org> changed:

           What    |Removed                     |Added
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             Status|New                         |Open
                 CC|                            |markj@FreeBSD.org

--- Comment #6 from Mark Johnston <markj@FreeBSD.org> ---
Is this still a problem on supported releases?  A few years ago I fixed a few
scheduler race conditions, mostly in ULE, that caused cores to go idle even
with pending work.

I tried running this on a 16-core AMD 7950X3D with hyperthreading enabled, and
don't see much variance:

git (main) markj@xinde> for i in $(seq 1 10); do t; done
1048576000 bytes transferred in 4.312122 secs (243169371 bytes/sec)
1048576000 bytes transferred in 4.062625 secs (258103089 bytes/sec)
1048576000 bytes transferred in 4.081073 secs (256936378 bytes/sec)
1048576000 bytes transferred in 4.017203 secs (261021443 bytes/sec)
1048576000 bytes transferred in 4.118516 secs (254600457 bytes/sec)
1048576000 bytes transferred in 4.063185 secs (258067483 bytes/sec)
1048576000 bytes transferred in 4.067748 secs (257778022 bytes/sec)
1048576000 bytes transferred in 4.484794 secs (233806939 bytes/sec)
1048576000 bytes transferred in 4.207453 secs (249218714 bytes/sec)
1048576000 bytes transferred in 3.954746 secs (265143670 bytes/sec)

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