ACPI slowing CPU... or something else

[Garrett Cooper]

V.I.Victor wrote:
>  I've two 5.4 desktop boxes.  Pretty much the same installation; both
>  from the same CD, same apps, no monitor/keyboard, 1-user logged-on via
>  ssh (command-line only w/no gui) and otherwise lightly loaded.
>
>  Box_A: CPU: AMD-K7(tm) Processor (598.84-MHz 686-class CPU)
>         avail memory = 121630720 (115 MB)
>         ACPI disabled by blacklist.
>
>  Box_B: CPU: Intel(R) Pentium(R) 4 CPU 1.80GHz (1794.19-MHz 686-class CPU)
>         avail memory = 252186624 (240 MB)
>         cpu0: <ACPI CPU> on acpi0
>         acpi_throttle0: <ACPI CPU Throttling> on cpu0
>
>  When running the following segment of a small gawk program:
>
>      cnt=0; s=systime(); while(s==systime()) ; # next second
>      s=systime(); while(s==systime()) cnt++; # count for 1-sec
>
>  Box_A(600M) always reports 'cnt' between 310000 to 320000.
>
>  Box_B(1800M) has been as low as 167000 and never higher than 254000.
>
>  So -- Box_B is 3-times faster than Box_A but runs the segment (at
>  best) about 20% more slowly!
>
>  Yesterday was when I saw the Box_B(1800M) 167000-ish numbers.  Today
>  after seeing an increase to the 250000-ish numbers, I started to
>  read-up on ACPI.
>
>  sysctl -a | grep cpu.*freq reports:
>
>  dev.cpu.0.freq: 1796
>  dev.cpu.0.freq_levels: 1796/-1 1571/-1 1347/-1 1122/-1 898/-1 \
>                         673/-1 449/-1 224/-1
>  dev.cpufreq.0.%driver: cpufreq
>  dev.cpufreq.0.%parent: cpu0
>
>  If I understand the 'sysctl' output, Box_B is running (now) at
>  1796-MHz.  And for Box_B cnt==252433; for Box_A cnt==318942.
>
>  Any opinions on what's going on and/or what I'm not understanding?
>
>  Thanks!
>   
Yes. On my virtual machine with ACPI:

dev.cpu.0.freq: 2653
dev.cpu.0.freq_levels: 2653/-1 2321/-1 1989/-1 1658/-1 1326/-1 994/-1 
663/-1 331/-1

[root at optimus-vm-7 ~]# dmesg | grep 26
FreeBSD 7.0-CURRENT #5: Tue Jul 17 08:22:26 UTC 2007
CPU: Intel(R) Core(TM)2 CPU          6700  @ 2.66GHz (2666.79-MHz 
K8-class CPU)
Timecounter "TSC" frequency 2666794890 Hz quality 800

What are the following sysctls set to?

kern.clockrate
hw.acpi.cpu.cx_lowest
dev.cpu.0.cx_lowest
dev.cpu.0.cx_usage

-Garrett