kern/140658: dev.cpu.0.cx_lowest=C3 from /etc/sysctl.conf or /boot/loader.conf does not apply at boot when cpufreq used as module outside kernel

[vermaden]

>Number:         140658
>Category:       kern
>Synopsis:       dev.cpu.0.cx_lowest=C3 from /etc/sysctl.conf or /boot/loader.conf does not apply at boot when cpufreq used as module outside kernel
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Wed Nov 18 07:20:02 UTC 2009
>Closed-Date:
>Last-Modified:
>Originator:     vermaden
>Release:        possible to recreate on 8.0-RC2/8.0-RC3
>Organization:
>Environment:
stock GENERIC kernel and GENERIC kernel rebuild without cpufreq in kernel config
>Description:
If you have cpufreq compiled into the kernel, then setting C-states
from /etc/sysctl.conf or /boot/loader.conf works as desired.

examples:
  /etc/sysctl.conf
  dev.cpu.0.cx_lowest=C2
  dev.cpu.0.cx_lowest=C3

  /boot/loader.conf
  cpufreq_load="YES"
  dev.cpu.0.cx_lowest=C2
  dev.cpu.0.cx_lowest=C3

When you tak cpufreq OUTSIDE the kernel, as a module, these
setting no longer apply after reboot, but you can manually set
them by sysctl(8) as usual.

Of course cpufreq is loaded at boot with cpufreq_load="YES" line in /boot/loader.conf
>How-To-Repeat:

>Fix:


>Release-Note:
>Audit-Trail:
>Unformatted: