Arch Linux

imrehg

Member

From: Taipei, TW

Registered: 2008-04-10

Posts: 96

Amarok eliminates C3 processor states?

Hi,

  I'm running Archlinux on EeePC, and it works great, most of the time.
  Tried to tweak the system to have lower power consumption, and run a few tests with PowerTOP 1.9

  PowerTOP reports all C0-C3 states, and plenty of time it stays as low as C3 (could get 2.3 wakeups from idle with 760ms average residency there).
  But one weird thing:
  After I start Amarok (in Xfce4), the processor doesn't ever go lower than C2. Even after Amarok finished, even when exiting back to the console, just C2, never down to C2....

  Is there any reason, why it should happen?

  I haven't tried many other programs yet, whether they have similar effect. I know, though, that the linux_uvc driver doesn't let the CPU to C3 state either (for this test, I removed the linux_uvc driver, and it was clocking down before starting Amarok).

  Cheers,
     Greg

imrehg

Member

From: Taipei, TW

Registered: 2008-04-10

Posts: 96

Re: Amarok eliminates C3 processor states?

....
though, upon further testing (I know I should have checked it before), it seems to be more of a gstreamer problem....

I tried Amarok with SomaFM. Now, if I use directly gst-launch-0.10 after boot on the console, it behaves the same: no C3 state anymore, even after exiting....

While running gst-launch-0.10, it appears on the wapeups list, with "schedule_timeout (process_timeout)" and "sk_reset_timer (tcp_delack_timer)". Can it set something in the linux network handling, that causes the C3 not being available anymore?

imrehg

Member

From: Taipei, TW

Registered: 2008-04-10

Posts: 96

Re: Amarok eliminates C3 processor states?

Well, okay, it's kinda bad, but I'll answer my own question in the end....

The very source of the problem was the snd_hda_intel High-Definition Audio driver in the kernel. Whenever I played any music (amarok, gstreamer, mpg123,...) the CPU never returned to the C3 level.

However, this was because even if the power-saving was compiled into the kernel module, it was disabled:

     [*]   Aggressive power-saving on HD-audio
     (0)     Default time-out for HD-audio power-save mode

So, after manually enabling the power-saving:

[root@eeepc ~]# cd /sys
[root@eeepc sys]# find -name power_save
./module/snd_hda_intel/parameters/power_save
[root@eeepc sys]# echo 1 > module/snd_hda_intel/parameters/power_save
[root@eeepc sys]#

sure, the whole command can be compressed into:

 echo 1 > `find /sys -name power_save`

- now after the music stopped in any, the system returns to the lower C3 state.
Great, more power-saving (now it would be just brilliant to do something about the uvcvideo's similar issue....