Date: Sun, 19 Dec 2021 16:07:34 +0000 From: bugzilla-noreply@freebsd.org To: bugs@FreeBSD.org Subject: [Bug 254040] AMD 5950X hyperthreading strange performance swings Message-ID: <bug-254040-227-D8OA2j4STH@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 #3 from Stefan E=C3=9Fer <se@FreeBSD.org> --- Update after booting a kernel with SCHED_4BSD: This really appears to be a SCHED_ULE issue, as expected. With SCHED_4BSD t= he results are quite homogeneous for each run: $ t # repeated runs ... 1048576000 bytes transferred in 6.720101 secs (156035746 bytes/sec) s048576000 bytes transferred in 7.037620 secs (148995835 bytes/sec) 1048576000 bytes transferred in 7.031251 secs (149130790 bytes/sec) 1048576000 bytes transferred in 7.032412 secs (149106159 bytes/sec) 1048576000 bytes transferred in 7.202687 secs (145581229 bytes/sec) 1048576000 bytes transferred in 6.918272 secs (151566177 bytes/sec) 1048576000 bytes transferred in 6.391244 secs (164064463 bytes/sec) 1048576000 bytes transferred in 6.686209 secs (156826683 bytes/sec) 1048576000 bytes transferred in 6.668778 secs (157236600 bytes/sec) 1048576000 bytes transferred in 6.914906 secs (151639959 bytes/sec) 1048576000 bytes transferred in 6.835760 secs (153395678 bytes/sec) 1048576000 bytes transferred in 6.755348 secs (155221619 bytes/sec) $ t 4 1048576000 bytes transferred in 7.574533 secs (138434415 bytes/sec) 1048576000 bytes transferred in 7.776473 secs (134839540 bytes/sec) 1048576000 bytes transferred in 7.839487 secs (133755689 bytes/sec) 1048576000 bytes transferred in 7.856730 secs (133462132 bytes/sec) $ t 4 1048576000 bytes transferred in 7.481412 secs (140157499 bytes/sec) 1048576000 bytes transferred in 7.557077 secs (138754182 bytes/sec) 1048576000 bytes transferred in 7.676920 secs (136588110 bytes/sec) 1048576000 bytes transferred in 8.040430 secs (130412922 bytes/sec) $ t 4 1048576000 bytes transferred in 7.484386 secs (140101810 bytes/sec) 1048576000 bytes transferred in 7.581198 secs (138312698 bytes/sec) 1048576000 bytes transferred in 7.710614 secs (135991248 bytes/sec) 1048576000 bytes transferred in 7.736921 secs (135528856 bytes/sec) $ t 16 1048576000 bytes transferred in 9.879846 secs (106132833 bytes/sec) 1048576000 bytes transferred in 10.087562 secs (103947418 bytes/sec) 1048576000 bytes transferred in 10.232516 secs (102474894 bytes/sec) 1048576000 bytes transferred in 10.237664 secs (102423370 bytes/sec) 1048576000 bytes transferred in 10.320563 secs (101600658 bytes/sec) 1048576000 bytes transferred in 10.375758 secs (101060179 bytes/sec) 1048576000 bytes transferred in 10.443859 secs (100401199 bytes/sec) 1048576000 bytes transferred in 10.481844 secs (100037355 bytes/sec) 1048576000 bytes transferred in 10.494019 secs (99921294 bytes/sec) 1048576000 bytes transferred in 10.510178 secs (99767674 bytes/sec) 1048576000 bytes transferred in 10.559435 secs (99302286 bytes/sec) 1048576000 bytes transferred in 10.638978 secs (98559840 bytes/sec) 1048576000 bytes transferred in 10.678294 secs (98196963 bytes/sec) 1048576000 bytes transferred in 10.808183 secs (97016860 bytes/sec) 1048576000 bytes transferred in 11.084706 secs (94596647 bytes/sec) 1048576000 bytes transferred in 11.231343 secs (93361587 bytes/sec) Seems that my BIOS settings were not optimal during the tests documented in Comment 2. After loading "Optimal Default" settings and re-activation of the energy efficiency options I do get the following sysctl output now: $ sysctl dev.cpu.0 dev.cpu.0.temperature: 29,6C dev.cpu.0.cx_method: C1/hlt C2/io dev.cpu.0.cx_usage_counters: 180 70723 dev.cpu.0.cx_usage: 0.25% 99.74% last 9261us dev.cpu.0.cx_lowest: C8 dev.cpu.0.cx_supported: C1/1/1 C2/2/18 dev.cpu.0.freq_levels: 3400/3740 2800/2800 2200/1980 dev.cpu.0.freq: 3400 dev.cpu.0.%parent: acpi0 dev.cpu.0.%pnpinfo: _HID=3DACPI0007 _UID=3D0 _CID=3Dnone dev.cpu.0.%location: handle=3D\_SB_.PLTF.C000 dev.cpu.0.%driver: cpu dev.cpu.0.%desc: ACPI CPU Anyway, after another reboot back to SCHED_ULE and repeating the tests with= new BIOS settings I see: $ t 1 # multiple runs again ... 1048576000 bytes transferred in 7.640816 secs (137233502 bytes/sec) 1048576000 bytes transferred in 6.225996 secs (168418995 bytes/sec) 1048576000 bytes transferred in 4.852763 secs (216078118 bytes/sec) 1048576000 bytes transferred in 4.832574 secs (216980866 bytes/sec) 1048576000 bytes transferred in 4.819031 secs (217590617 bytes/sec) $ t 4 1048576000 bytes transferred in 4.956440 secs (211558309 bytes/sec) 1048576000 bytes transferred in 7.634614 secs (137344998 bytes/sec) 1048576000 bytes transferred in 7.788965 secs (134623280 bytes/sec) 1048576000 bytes transferred in 7.819442 secs (134098574 bytes/sec) $ t 4 1048576000 bytes transferred in 4.853663 secs (216038083 bytes/sec) 1048576000 bytes transferred in 4.857143 secs (215883287 bytes/sec) 1048576000 bytes transferred in 7.721846 secs (135793430 bytes/sec) 1048576000 bytes transferred in 7.792580 secs (134560821 bytes/sec) $ t 4 1048576000 bytes transferred in 4.908570 secs (213621479 bytes/sec) 1048576000 bytes transferred in 7.742029 secs (135439433 bytes/sec) 1048576000 bytes transferred in 7.784341 secs (134703245 bytes/sec) 1048576000 bytes transferred in 7.794096 secs (134534649 bytes/sec) Very similar to the results in the initial bug report ... And it really shows that SCHED_ULE causes the incoherent performance.=20 But the throughput with SCHED_ULE is a lot higher than with SCHED_4BSD, probably due to the immensely higher system overhead of the latter with a l= arge number of cores. While the CPU% with SCHED_ULE is in the order of 2%, with SCHED_4BSD I have seen values up to 60% with 32 parallel tasks. Another observation: WCPU of the bzip2 processes on the kernel with SCHED_4= BSD was displayed as way beyond 100% (in the order of 300% in one run I remembe= r). Since bzip2 is not multi-threaded (AFAIK) this seems to be a wrong measurem= ent. The CPU% for the bzip2 processes is always near 100% with SCHED_ULE. --=20 You are receiving this mail because: You are the assignee for the bug.=
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