Re: weird ktrace timestamps?

[der Mouse <mouse%Rodents-Montreal.ORG@localhost>]

>> There are two interesting things here: the timestamps in the file do
>> not warp backwards by almost two seconds - but they do warp
>> backwards, by 3353 ns.
> Try a different time counter.  See kern.timecounter.

kern.timecounter.choice = clockinterrupt(q=0, f=100 Hz) TSC(q=-100, 
f=1795636350 Hz) ACPI-Fast(q=1000, f=3579545 Hz) i8254(q=100, f=1193182 Hz) 
dummy(q=-1000000, f=1000000 Hz)
kern.timecounter.hardware = ACPI-Fast
kern.timecounter.timestepwarnings = 0

I switched to TSC and got the same syndrome (well, as far as kdump
output goes; I didn't dig into ktrace.out).  Switching to
clockinterrupt made the syndrome go away, but all the timestamp deltas
printed by kdump -R were zero (there probably were a very few that
weren't, but I didn't see any of them in a quick eyeball skim).

> Is this UP or MP?

MP.

cpu0 at mainbus0: apid 0 (boot processor)
cpu0: Intel Core 2 (Merom) (686-class), 1795.62 MHz, id 0x6fd
cpu0: features bfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR>
cpu0: features bfebfbff<PGE,MCA,CMOV,PAT,PSE36,CFLUSH,DS,ACPI,MMX>
cpu0: features bfebfbff<FXSR,SSE,SSE2,SS,HTT,TM,SBF>
cpu0: features2 e3bd<SSE3,MONITOR,DS-CPL,VMX,EST,TM2,xTPR>
cpu0: "Intel(R) Core(TM)2 Duo CPU     T7100  @ 1.80GHz"
cpu0: I-cache 32 KB 64B/line 8-way, D-cache 32 KB 64B/line 8-way
cpu0: L2 cache 2 MB 64B/line 8-way
cpu0: using thermal monitor 1
cpu0: Enhanced SpeedStep (1420 mV) 2000 MHz
cpu0: unknown Enhanced SpeedStep CPU.
cpu0: using only highest and lowest power states.
cpu0: Enhanced SpeedStep frequencies available (MHz): 2000 1200
cpu0: calibrating local timer
cpu0: apic clock running at 199 MHz
cpu0: 64 page colors
cpu1 at mainbus0: apid 1 (application processor)
cpu1: starting
cpu1: Intel Core 2 (Merom) (686-class), 1795.43 MHz, id 0x6fd
cpu1: features bfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR>
cpu1: features bfebfbff<PGE,MCA,CMOV,PAT,PSE36,CFLUSH,DS,ACPI,MMX>
cpu1: features bfebfbff<FXSR,SSE,SSE2,SS,HTT,TM,SBF>
cpu1: features2 e3bd<SSE3,MONITOR,DS-CPL,VMX,EST,TM2,xTPR>
cpu1: "Intel(R) Core(TM)2 Duo CPU     T7100  @ 1.80GHz"
cpu1: I-cache 32 KB 64B/line 8-way, D-cache 32 KB 64B/line 8-way
cpu1: L2 cache 2 MB 64B/line 8-way
cpu1: using thermal monitor 1

I did consider the possibility that MP was relevant, but it strikes me
as highly unlikely that it would migrate between processors exactly
there every time (and, apparently, _only_ there).

Is it likely enough that it's something else tied to MPness that it's
worth trying a test under a UP kernel?

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