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# I am not the only one using an AMD who has this problem | |
# https://www.reddit.com/r/linuxquestions/comments/ts1hgw/zen_3_tsc_unstable_which_part_to_blame | |
# Maybe kernel changes made it worse, and now might make it better | |
# https://lore.kernel.org/lkml/20211027164352.GA23273@incl/ | |
# And more via https://www.google.com/search?q=amd+read_hpet | |
# Output from "perf top" on slower system -> why is read_hpet.part.0 using so much CPU | |
Samples: 59K of event 'cycles', 4000 Hz, Event count (approx.): 29054393413 lost: 0/0 drop: 0/0 | |
Overhead Shared Object Symbol | |
43.08% [kernel] [k] read_hpet.part.0 | |
1.82% [kernel] [k] psi_group_change | |
1.45% [kernel] [k] copy_user_generic_string | |
# slower system | |
[ 2.164887] clocksource: timekeeping watchdog on CPU3: Marking clocksource 'tsc' as unstable because the skew is too large: | |
[ 2.164903] clocksource: 'hpet' wd_nsec: 511824407 wd_now: 1bfd1b4 wd_last: 14fff2a mask: ffffffff | |
[ 2.164913] clocksource: 'tsc' cs_nsec: 507936081 cs_now: 941afb6f4 cs_last: 904c95d80 mask: ffffffffffffffff | |
[ 2.164921] clocksource: 'tsc' is current clocksource. | |
[ 2.164932] tsc: Marking TSC unstable due to clocksource watchdog | |
[ 2.164947] TSC found unstable after boot, most likely due to broken BIOS. Use 'tsc=unstable'. | |
[ 2.164953] sched_clock: Marking unstable (2164461887, 485058)<-(2168194753, -3247949) | |
[ 2.165100] clocksource: Checking clocksource tsc synchronization from CPU 3 to CPUs 0-2. | |
[ 2.614948] clocksource: Switched to clocksource hpet | |
# faster system | |
[ 1.352218] tsc: Refined TSC clocksource calibration: 1996.248 MHz | |
[ 1.352239] clocksource: tsc: mask: 0xffffffffffffffff max_cycles: 0x398cac3bdaf, max_idle_ns: 881590646346 ns | |
[ 1.352300] clocksource: Switched to clocksource tsc | |
# slower system after: | |
1) edit /etc/default/grub -> GRUB_CMDLINE_LINUX_DEFAULT="clocksource=tsc tsc=reliable" | |
2) update-grub | |
3) reboot | |
[ 0.000000] Command line: BOOT_IMAGE=/boot/vmlinuz-5.15.0-52-generic root=UUID=b74a55d4-c21f-461b-924e-ce580094c502 ro clocksource=tsc tsc=reliable | |
[ 0.000000] tsc: Fast TSC calibration using PIT | |
[ 0.000000] tsc: Detected 1996.316 MHz processor | |
[ 0.045873] Kernel command line: BOOT_IMAGE=/boot/vmlinuz-5.15.0-52-generic root=UUID=b74a55d4-c21f-461b-924e-ce580094c502 ro clocksource=tsc tsc=reliable | |
[ 0.135487] clocksource: tsc-early: mask: 0xffffffffffffffff max_cycles: 0x398d2ccd6f0, max_idle_ns: 881590761034 ns | |
[ 0.328800] clocksource: Switched to clocksource tsc-early | |
[ 1.359537] tsc: Refined TSC clocksource calibration: 2011.757 MHz | |
[ 1.359559] clocksource: tsc: mask: 0xffffffffffffffff max_cycles: 0x1cff90860c8, max_idle_ns: 440795227807 ns | |
[ 1.359609] clocksource: Switched to clocksource tsc |
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