incorrect usleep/select delays with HZ > 2500

[John Baldwin]

On Sunday 06 September 2009 11:51:54 am Luigi Rizzo wrote:
> [Note 3] the TSC frequency is computed reading the tsc around a
>         call to DELAY(1000000) and assuming that the i8254 runs
>         at the nominal rate, 1.193182 MHz.
>         From tests I have made, the measurement in init_TSC() returns
>         a large error when HZ is large, whereas repeating the measurement
>         at a later time returns a much more reliable value.
>         As an example, see the following:
> 
>     Sep  6 14:21:59 lr kernel: TSC clock: at init_TSC 2323045616 Hz
>     Sep  6 14:21:59 lr kernel: 
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>
>     Sep  6 14:21:59 lr kernel: AMD 
Features=0xea500800<SYSCALL,NX,MMX+,FFXSR,RDTSCP,LM,3DNow!+,3DNow!>
>     Sep  6 14:21:59 lr kernel: TSC: P-state invariant
>     Sep  6 14:21:59 lr kernel: TSC clock: at cpu_startup_end 2323056910 Hz
>     Sep  6 14:21:59 lr kernel: TSC clock: at acpi_timer_probe 2311254060 Hz
>     Sep  6 14:21:59 lr kernel: TSC clock: at acpi_timer_probe_2 2311191310 
Hz
>     Sep  6 14:21:59 lr kernel: TSC clock: at pn_probe_start 2300822648 Hz
>     Sep  6 14:21:59 lr kernel: TSC clock: at pn_attach_start 2300830946 Hz
>     Sep  6 14:21:59 lr kernel: TSC clock: at pn_probe_start 2300840133 Hz
>     Sep  6 14:21:59 lr kernel: TSC clock: at pn_attach_start 2300835253 Hz
>     Sep  6 14:21:59 lr kernel: TSC clock: at lapic_setup_clock 2300868376 Hz
> 
>         The latter values are close to what is reported when HZ=1000.

Try disabling legacy USB support in the BIOS to see if an SMI# is firing 
during the DELAY() causing the TSC freq to be too high.  I have seen the USB 
legacy support cause this in other machines.
 
-- 
John Baldwin