Question on timecounter hardware / What cpu flag is constant_tsc
Mark Saad
nonesuch at longcount.org
Thu Feb 21 18:04:40 UTC 2013
All
I am looking into an issue with timecounter hardware on a number of HP
DL165 G7's
They all run FreeBSD 9.1-RELEASE and all have the same CPU and firmware.
However they report strange results when you probe kern.timecounter.choice
and
kern.timecounter.hardware
Take this example
ssh root at ssr4 "sysctl kern.timecounter.choice"
kern.timecounter.choice: TSC-low(-100) ACPI-safe(850) HPET(950) i8254(0)
dummy(-1000000)
ssh root at ssr4 "sysctl kern.timecounter.hardware"
kern.timecounter.hardware: HPET
dmidecode -s processor-version
AMD Opteron(TM) Processor 6212
dmidecode -s processor-frequency
2600 MHz
Unknown
from dmesg.boot
CPU: AMD Opteron(TM) Processor 6212 (2600.06-MHz K8-class
CPU)
Origin = "AuthenticAMD" Id = 0x600f12 Family = 15 Model = 1 Stepping
= 2
Features=0x178bfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,MMX,FXSR,SSE,SSE2,HTT>
Features2=0x1e98220b<SSE3,PCLMULQDQ,MON,SSSE3,CX16,SSE4.1,SSE4.2,POPCNT,AESNI,XSAVE,OSXSAVE,AVX>
AMD Features=0x2e500800<SYSCALL,NX,MMX+,FFXSR,Page1GB,RDTSCP,LM>
AMD
Features2=0x1c9bfff<LAHF,CMP,SVM,ExtAPIC,CR8,ABM,SSE4A,MAS,Prefetch,OSVW,IBS,XOP,SKINIT,WDT,LWP,FMA4,NodeId,Topology,<b23>,<b2
4>>
vs
ssh root at ssr3 "sysctl kern.timecounter.choice"
kern.timecounter.choice: TSC-low(1000) ACPI-safe(850) HPET(950) i8254(0)
dummy(-1000000)
ssh root at ssr3 "sysctl kern.timecounter.hardware"
kern.timecounter.hardware: TSC-low
dmidecode -s processor-version
AMD Opteron(TM) Processor 6212
dmidecode -s processor-frequency
2600 MHz
Unknown
from dmesg.boot
CPU: AMD Opteron(TM) Processor 6212 (2600.06-MHz K8-class
CPU)
Origin = "AuthenticAMD" Id = 0x600f12 Family = 15 Model = 1 Stepping
= 2
Features=0x178bfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,MMX,FXSR,SSE,SSE2,HTT>
Features2=0x1e98220b<SSE3,PCLMULQDQ,MON,SSSE3,CX16,SSE4.1,SSE4.2,POPCNT,AESNI,XSAVE,OSXSAVE,AVX>
AMD Features=0x2e500800<SYSCALL,NX,MMX+,FFXSR,Page1GB,RDTSCP,LM>
AMD
Features2=0x1c9bfff<LAHF,CMP,SVM,ExtAPIC,CR8,ABM,SSE4A,MAS,Prefetch,OSVW,IBS,XOP,SKINIT,WDT,LWP,FMA4,NodeId,Topology,<b23>,<b2
4>>
So my questions, what is the preferred time counter here ? In linux using
TSC is preferred over hpet and to tell if you have a trusted TSC your cpu
needs to support feature constant_tsc . Does anyone know what cpu feature
this is; is it listed in my a fore mentioned dmesg.boot feature lists ?
TIA
--
mark saad | nonesuch at longcount.org
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