[OmniOS-discuss] [discuss] illumos power management

[Paul B. Henson]

On 11/13/2013 9:10 AM, Rafael Vanoni wrote:

> Yes, If you don't specify individual settings for devices,
> "system-threshold always-on" will leave everything at full power.

Other than the CPU? IE, would the following:

autopm                  enable
system-threshold        always-on
cpupm                   enable

result in a system that manages CPU power, but leaves everything else 
always hot? I think that's what I'll probably go with for now.

> I don't know of a specific way of querying PM capabilities for
> devices, but have a look at the man page for power.conf(4). It
> mentions a way of specifying policies based on generic capabilities
> that can apply to any device that supports it, instead of having to do
> it one by one.

I don't see a way to do that for specifying threshold/timeouts, only the 
device-thresholds parameter, which takes a single specific device seems 
to allow specifying those. There is the device-dependency-property, 
which allows you to use generic capabilities, but only to define 
dependencies, not configure thresholds, the example is:

device-dependency-property removable-media /dev/fb

which evidentally means never power down a removable media device if the 
frame buffer is powered on.

I think most likely the only devices that are capable of being power 
managed in my server are the CPU and hard drives, but it would be nice 
to be able to confirm that.

> If the system supports it (essentially if we're able to create CPU
> power domains with information from ACPI tables), event mode is the
> default. Otherwise we fall back to polling.

Is there any way to tell what it ended up doing? I assume my box is new 
enough to support event mode, but you never know if the bios has broken 
ACPI data 8-/...

The options for cpu_deep_idle seem a bit confusing, there is "default" 
which says "Advanced  cpu  idle  power  saving  features  are enabled 
on  hardware  which  supports it", and "enable", which says "Enables the 
system to automatically use idle cpu power saving features" -- I'm not 
clear what the difference is here. You can't really enable a feature on 
hardware that doesn't support it ;). The third option "disable" makes 
sense, it won't do it regardless of whether or not the hardware could. 
Evidently if you don't specify it at all it defaults to "default", 
overall it seems it would be simpler for the only option for this 
parameter to be "disabled"; either it will do it if it can, or it won't 
do it at all if you tell it not to.

Thanks…