[OmniOS-discuss] [discuss] illumos power management

[Paul B. Henson]

> From: Rafael Vanoni [mailto:rafael.vanoni at pluribusnetworks.com]
> Sent: Thursday, November 14, 2013 10:33 AM
>
> # echo "cpupm::print" | mdb -k

2 (PM_CPUPM_EVENT)

Cool, looks like I'm good, thanks :).

> I think the default option refers to when you don't specify
> cpu_deep_idle at all, which is equivalent to having it and 'enable'.
> If you enable and the hardware doesn't support it, the OS falls back
> to whatever it can.

No, that's not what the man page reads as (excerpted below), at least to my
eyes. In checking the source code, looks like "disable", "enable", and
"default" are all valid to explicitly specify
(https://github.com/illumos/illumos-gate/blob/7256a34efe9df75b638b9e812912ef
7c5c68e208/usr/src/cmd/power/handlers.c), and "default" is exactly the same
as "enable" -- "Default policy is same as enable"
(https://github.com/illumos/illumos-gate/blob/7256a34efe9df75b638b9e812912ef
7c5c68e208/usr/src/uts/i86pc/os/cpupm/cpu_idle.c). So if you don't mention
it at all, it is the same as "default" which is the same as "enable". Seems
it would be simpler to only have one option, disable, but at least now I
understand what it's doing.

Thanks much.

---------
     If supported by the platform, a cpu_deep_idle entry  can  be
     used  to enable or disable automatic use of power saving cpu
     idle states. The format of the cpu_deep_idle entry is:

       cpu_deep_idle behavior

     Acceptable values for behavior are:

     default
                Advanced  cpu  idle  power  saving  features  are
                enabled  on  hardware  which  supports it. On X86
                systems this can translate to the use of ACPI  C-
                States beyond C1.

     enable
                Enables the system to automatically use idle  cpu
                power saving features.

     disable
                The system does not automatically  use  idle  cpu
                power  saving  features.  This option can be used
                when  maximum  performance  is  required  at  the
                expense of power.

Illumos             Last change: Feb 27, 2009                   7

File Formats                                        POWER.CONF(4)

     absent
                It  the  cpu_deep_idle  keyword  is  absent  from
                power.conf  the  behavior  is  the  same  as  the
                default case.