On Wed, 13 Nov 2013, Paul B. Henson wrote:
On 11/13/2013 11:24 AM, Garrett D'Amore wrote:
CPU power management is unlikely to do much for you. Its better to rely
on C-states to save power on modern systems.
I'm not sure how to interpret that; the power.conf man page says that if
cpu_deep_idle is enabled "On X86 systems this can translate to the use of
ACPI C-States beyond C1", so it seems illumos is already using C states for
CPU power management?
Indeed.
Frankly, very very few components on typical illumos based
systems even support power management apart from the disk subsystem.
Probably only disks and CPU I would think, although it would be nice to be
able to list out what the system thinks it could manage. I definitely don't
want to spin down the disks, but I wouldn't mind saving a few watts here and
there on the CPU. So maybe something like:
autopm disable
autoS3 disable
cpupm enable
cpu_deep_idle enable
CPUPM can be independent of autopm, so if you desire CPUPM and not disk
PM, setting autopm to 'disable' is correct (note, autoS3 is only relevant
if S3-support is 'enable'). Also, "cpupm" can take 2 arguments, the
second being one of 'event-mode' or 'poll-mode' (the default being
'event-mode', which is the mode that is separated from autopm). So you
might wish to change 'cpupm enable' to 'cpupm enable event-mode' just so
it is explicit (you might also wish to add 'S3-support disable' just to
make sure the system won't ever try to suspend).
Also, you *can* specify different PM capabilities for different disks.
Multi-terabyte drives are cheap, and could serve as the backup media.
There could well be value of having backup disks spindown, but keep the OS
disks always-on (you would have to enable autopm for this action, though).
Lastly, powertop(1m) can be used to see how well CPUPM is working for you.
The display subsystem typically uses its own power management which
doesn't participate with the rest of illumos' power management
framework, IIRC.)
I am not aware of any x86 display drivers that have a power(9e) entry
point, but if it does, it will partake in the PM framework operations.
Unlike good old SPARC boxes, my x86 "headless" server has a graphics adapter
in it. As I'm using a serial console, all it ever displays after boot is a
blank screen, can't imagine it takes much power...
It may be more than you might think. The backlight on flat panels is
the biggest draw, and may not be trivial. A monitor rendering black will
still have the gun scanning and the tube lit. You might prefer either
removing the display adapter, unplugging the monitor, or starting X so
that it can run display PM.
Cheers!
---- Randy
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