TSC as timecounter makes system lag

Jia-Shiun Li jiashiun at gmail.com
Fri Jan 13 00:26:36 UTC 2017

Hi all,

since 2 or 3 weeks ago, I noticed that my old Penryn-based Intel Pentium
T4200 notebook lagged a lot. System time was running a lot slower,
sometimes even looked like it freezed. Keystroke repeat rate was slow too.

Since system time is slow, I tried to change timecounter from default TSC
to HPET. And it resumed normal immediately.

The same world binary works fine on other Ivybridge and Haswell desktops,
so I assume this may be related to CPU or mainboard generations.

version is

FreeBSD jsli-nb 12.0-CURRENT FreeBSD 12.0-CURRENT #0 r311687: Mon Jan  9
04:07:27 CST 2017
jsli at 4cbsd:/personal/freebsd/obj/x64/personal/freebsd/fbsdsrc/sys/MINIMAL-NODEBUG

and CPU is

CPU: Pentium(R) Dual-Core CPU       T4200  @ 2.00GHz (1995.04-MHz K8-class
  Origin="GenuineIntel"  Id=0x1067a  Family=0x6  Model=0x17  Stepping=10


  AMD Features=0x20100800<SYSCALL,NX,LM>
  AMD Features2=0x1<LAHF>
  TSC: P-state invariant, performance statistics

Tested similar OS rev on another Intel Core 2 Duo E7400 Wolfdale (the same
generation as the Pentium T4200). The same lag also happens on it.

BTW on both system, cpuX:timer interrupts do not fire at all and count
remains 0.


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