TSC as timecounter makes system lag

[Jia-Shiun Li]

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
amd64

and CPU is

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

Features=0xbfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>

Features2=0xc00e39d<SSE3,DTES64,MON,DS_CPL,EST,TM2,SSSE3,CX16,xTPR,PDCM,XSAVE,OSXSAVE>
  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.

-Jia-Shiun