[Bug 254040] AMD 5950X hyperthreading strange performance swings

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

--- Comment #5 from Andriy Gapon <avg@FreeBSD.org> ---
And a possible "eureka moment" that's consistent with the original description:
if I choose odd logical CPUs, (cpuset -l $((2 * i + 1)), then I consistently
get the worst results:
$ ~/test.sh 4
1048576000 bytes transferred in 7.800822 secs (134418651 bytes/sec)
1048576000 bytes transferred in 7.803095 secs (134379498 bytes/sec)
1048576000 bytes transferred in 7.809778 secs (134264513 bytes/sec)
1048576000 bytes transferred in 7.810560 secs (134251064 bytes/sec)

If this is indeed what it is, then several conclusions can be drawn:
- hardware threads within a core are not born equal on this hardware
- "primary" threads should be preferred
- ULE does not do that

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