Hi there,
All my tests were done on systems that have only one graphics card or
have on board graphics only. No options to optimize anything there.
Although: in x86 server systems: why even use a graphics card while a
serial connection is sufficient ?
But that's proably another story as these motherboards are hardly
available (at least for a common x86 system for a competitive price)
Disabling the integrated graphics adapter in the bios is no option on
the motherboards I have.
As far as KMS is concerned: Just after I sent my mail to your discussion
list I started reading about it and gave it a try on a desktop with an
ati IGP.
I think the results are disappointing. Since kernel 2.6.35 there is
inital kms power management support for ati and it saves 3 watt for me.
that's 7 watt less saving than my method using the proprietary driver
and turning (all) screens off using xrandr.
I do not know how nvidia performs, but it seems indeed that the intel
graphics adapter does proper powersaving after enabling KMS (turning off
the screen using xrandr does not save more anyway).
Tests I did with the intel adapter were done with a laptop though, so
perhaps I am comparing apples and oranges here.
Thanks for your replies. Reading about and testing with KMS was insightful.
Still have some testing to do regarding the intel graphics driver with
or without the framebuffer module. I have not had any decent results there!
regards,
Tobias.
On 08/17/2010 09:57 PM, Jesse Barnes wrote:
On Mon, 16 Aug 2010 21:11:04 +0300
Auke Kok<[email protected]> wrote:
On 08/15/2010 02:51 AM, tobias appelo wrote:
Hi there,
I was wondering what's the best way to reduce gpu power usage on a
server or desktop that is not required to run X. It appears to me that
this is still very common and I would like to save as much pwer as possible.
I did some testing on desktops / laptops with intel integrated graphics,
a desktop with an nvidia card and a desktop with an integrated ati video
card and in each case the amount of watts that the whole system used
(measured from wall) became less after initialization of X. (saved
around 5 watts).
Turning the monitor off using xrandr saved 5 watts more.
In case of the nvidia and ati card I used the proprietary driver as it
gave me better results when starting X.
Simply modprobing the graphis driver did not lower the amount of watts
used. Also, experimenting with underclockutilities such as rovclock or
nvclock did not produce the same amount of powersaving (only about 3
watts) as just starting X.
Currently I use a fluxbox setup to get the power usage as low as
possible (and xrandr automatically turns off the monitor using fluxbox
startup file), but I do not like installing all kinds of X software on
systems that do not require it. Is there another way to reduce the GPU
power usage in console mode ?
Well, you could remove the power-hungry graphics card alltogether. This
might be an option if the system has on-board graphics.
Intel's gfx chipsets will use kernel-modesetting which means that the
graphics chipset will be fully initialized at boot time and you'll get
the powersavings that way without running Xorg at all.
Right, loading the i915 driver with KMS enabled should reduce the power
usage to a lower level. Having all the VGA hardware enabled costs a
lot of power on recent chips; it's provided for compatibility only and
we don't put much effort into optimizing its power consumption.
A simple console will be missing support for framebuffer compression
though, so you won't see best case power consumption when you're using
fbcon with the i915 driver.
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