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#1 2013-02-15 17:38:53

johannesg00
Member
Registered: 2010-11-30
Posts: 36

High power usage of display backlight (Asus UX32VD)

Hallo,

i have an Asus UX32VD Laptop running ArchLinux.
Everything works fine after some tuning, but i have a high power usage of the Display backligt reported in powertop.

PowerTOP 2.1      Overview   Idle stats   Frequency stats   Device stats   Tunables                                     


The battery reports a discharge rate of 14.4 W
System baseline power is estimated at 4.59 W

Power est.    Usage     Device name
  3.08 W    100.0%        Display backlight
  1.57 W      0.0 pkts/s  Network interface: wlan0 (iwlwifi)
  1.57 W     60.0%        Display backlight
  1.57 W     41.9%        Display backlight
  658 mW     56.1 ops/s   GPU
  556 mW    100.0%        Radio device: iwlwifi
  307 mW     11.2%        CPU use
    0 mW    100.0%        Radio device: asus-nb-wmi
    0 mW      0.0%        USB device: USB2.0 HD UVC WebCam (Chicony Electronics Co.,Ltd.)
    0 mW      0.0%        USB device: EHCI Host Controller
    0 mW      0.0%        USB device: xHCI Host Controller
    0 mW      0.0%        USB device: xHCI Host Controller
    0 mW      0.0%        USB device: USB2.0-CRW (Generic)
    0 mW      0.0%        Radio device: asus-nb-wmi
    0 mW      0.0%        USB device: usb-device-8087-0024
    0 mW      0.0%        USB device: usb-device-8087-0024
    0 mW      0.0%        USB device: EHCI Host Controller
    0 mW      0.0%        Audio codec hwC0D0: Realtek
    0 mW      0.0%        Audio codec hwC0D3: Intel
            100.0%        PCI Device: Intel Corporation 3rd Gen Core processor Graphics Controller
            100.0%        PCI Device: Intel Corporation 7 Series/C210 Series Chipset Family MEI Controller #1
            100.0%        PCI Device: NVIDIA Corporation Device 1140
            100.0%        PCI Device: Intel Corporation Xeon E3-1200 v2/3rd Gen Core processor PCI Express Root Port
            100.0%        PCI Device: Intel Corporation 7 Series Chipset Family 6-port SATA Controller [AHCI mode]
            100.0%        PCI Device: Intel Corporation 7 Series/C210 Series Chipset Family PCI Express Root Port 2
            100.0%        PCI Device: Intel Corporation 7 Series/C210 Series Chipset Family High Definition Audio Controller
            100.0%        PCI Device: Intel Corporation HM76 Express Chipset LPC Controller
            100.0%        PCI Device: Intel Corporation Centrino Advanced-N 6235
              0.0%        PCI Device: Intel Corporation 7 Series/C210 Series Chipset Family USB Enhanced Host Controller #2
              0.0%        PCI Device: Intel Corporation 7 Series/C210 Series Chipset Family PCI Express Root Port 1
              0.0%        PCI Device: Intel Corporation 7 Series/C210 Series Chipset Family USB xHCI Host Controller
              0.0%        PCI Device: Intel Corporation 7 Series/C210 Series Chipset Family USB Enhanced Host Controller #1
              0.0%        PCI Device: Intel Corporation 3rd Gen Core Processor Thermal Subsystem
              0.0%        PCI Device: Intel Corporation 7 Series/C210 Series Chipset Family SMBus Controller

If i change the brightness of the display the power usage stays the same.
Does anybody have an idea whats wrong with it?

Johannes

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#2 2013-02-15 17:49:24

WonderWoofy
Member
From: Los Gatos, CA
Registered: 2012-05-19
Posts: 8,412

Re: High power usage of display backlight (Asus UX32VD)

Just to make sure, you are aware that powertop updates itself in intervals of maybe 10-15 seconds (not sure exactly), so after you change it, you should make sure that you refresh powertop.

Also I think that this could happen if you are using some kind of software brightness adjustment rather than something that actually changes the brightness through the /sys interface. How does your system handle brightness adjustment? Did you have to set it up? Hot keys? Muffins? Fairies?

In other words, is there. a module that handles the brightness keys, or are you changing the brightness through some application included with a DE?

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#3 2013-02-15 18:04:15

johannesg00
Member
Registered: 2010-11-30
Posts: 36

Re: High power usage of display backlight (Asus UX32VD)

I use the Fn Keys to change the brightness and it seems that this changes the /sys/class/backlight/intel_backlight/actual_brightness file, so this should be ok.
I tested it again and with lowest brightness i get this result:

  3.17 W    100.0%        Display backlight
  3.17 W    100.0%        Display backlight
  1.57 W      0.2%        Display backlight

and with highest setting:

  3.15 W    100.0%        Display backlight
  3.15 W    100.0%        Display backlight
  3.15 W    100.0%        Display backlight

This seems quite high... And i don't understand why display backlight is listed three times..

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#4 2013-05-29 07:13:51

airydragon
Member
Registered: 2011-09-24
Posts: 3

Re: High power usage of display backlight (Asus UX32VD)

I've fixed this by adding some kernel parameters. It works perfectly under gnome (both gnome-control-center -> power and https://aur.archlinux.org/packages/gnom … -pulbs-git ) Fn keys (F5 & F6) are not working yet.

Bios :

$ sudo dmidecode -s bios-version
UX32VD.212

Kernel :

$ uname -a
Linux aega 3.9.4-1-ARCH #1 SMP PREEMPT Sat May 25 16:14:55 CEST 2013 x86_64 GNU/Linux

I am using grub-efi-x86_64 as UEFI bootloader. Unfortunately I don't know how to set kernel parameters for other bootloaders. You may find different bootloaders' settings in the wiki.

change line in /etc/defaults/grub :

GRUB_CMDLINE_LINUX_DEFAULT="quiet acpi_osi='!Windows 2012' acpi_osi=Linux add_efi_memmap i915.i915_enable_rc6=1 pcie_aspm=force drm.vblankoffdelay=1 i915.semaphores=1 nmi_watchdog=0 acpi_backlight=vendor"

acpi_osi='!Windows 2012' acpi_osi=Linux order is important!

Finally generate grub configuration file via grub-mkconfig.

sudo grub-mkconfig -o /boot/efi/EFI/grub/grub.cfg

And reboot.

Results :

$ cat /sys/class/backlight/intel_backlight/actual_brightness 
421
PowerTOP 2.3      Overview   Idle stats   Frequency stats   Device stats   Tunables                                     


The battery reports a discharge rate of 7.55 W
System baseline power is estimated at 4.00 W

Power est.    Usage     Device name
  4.11 W     10.7%        CPU use
  988 mW    100.0%        Radio device: iwlwifi
  313 mW      9.8%        Display backlight
  162 mW      0.0%        Display backlight
 67.4 mW     22.5 ops/s   GPU
 58.3 mW      0.6 pkts/s  Network interface: wlp3s0 (iwlwifi)
$ cat /sys/class/backlight/intel_backlight/actual_brightness 
4302
PowerTOP 2.3      Overview   Idle stats   Frequency stats   Device stats   Tunables                                     


The battery reports a discharge rate of 12.0 W
System baseline power is estimated at 4.00 W

Power est.    Usage     Device name
  4.52 W     11.1%        CPU use
  2.31 W    100.0%        Display backlight
  2.31 W    100.0%        Display backlight
  1.06 W    100.0%        Radio device: iwlwifi
  322 mW    101.2 ops/s   GPU

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