Date: Tue, 21 Dec 2021 10:56:35 +0000 From: bugzilla-noreply@freebsd.org To: bugs@FreeBSD.org Subject: [Bug 254040] AMD 5950X hyperthreading strange performance swings Message-ID: <bug-254040-227-YTxsIWAKrd@https.bugs.freebsd.org/bugzilla/> In-Reply-To: <bug-254040-227@https.bugs.freebsd.org/bugzilla/> References: <bug-254040-227@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D254040 --- Comment #5 from Andriy Gapon <avg@FreeBSD.org> --- And a possible "eureka moment" that's consistent with the original descript= ion: 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 --=20 You are receiving this mail because: You are the assignee for the bug.=
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