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I am thinking about compiling the kernel in order to have a low consumption configuration ready for the raspberry.

Is there any configuration or .config created before compiling it with the power safe in mind to compile it?

Not expect a whole list but, any sugestions about the options that must be avoided or the ones that must be selected on make manuconfig before compiling it?

6

The kernel already consumes negligible power. The software loaded on the pi would be the ones munching the most power because of processor time (Apache, databases, networking, etc.)

Here are some tips to reduce power consumption even further:

  1. Disable unneeded software services on the Pi.
  2. Avoid unnecessary peripherals (USB devices, GPIO accessories)
  3. Shut down the USB controller and LAN chip using these commands: /etc/init.d/networking stop echo 0 > /sys/devices/platform/bcm2708_usb/buspower
  4. Undervolt and underclock the Pi by editing /boot/config.txt. Set the minimum ARM frequency to 250, minimum core frequency to 100, and minimum sdram_freq to 150.

  5. Disable the HDMI port using the command sudo /opt/vc/bin/tvservice -o

  6. For Raspberry Pi 2: Limit the amount of cores you'll use. Add maxcpus=N in /boot/cmdline.txt where "N" is the number of cores you want.
  • I was just being curious about getting a custom compiled kernel, with the proper options in the make menu like the ones in "Power management and ACPI options" or "Processor type and features -> Preemption Model" to sacrificate some processor performance. The tips that you have pointed are great, but can be done over the ones i am curious about making it even more less power consumption – Jesus Cepeda Jan 23 '16 at 12:07
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    The problem is the hardware itself has no power saving features, beyond being fairly low power to start with (I think a pi consumes < 5 watts on average). There is no ACPI to configure for. As PandaLion98 says, the kernel won't add to the power consumption all by itself. So there is nothing you can do to subtract from nothing. – goldilocks Jan 23 '16 at 12:21
  • Underclocking the RAM is an interesting tip. I believe a major difference between the pi and phones power consumption wise is the RAM; phone memory has low power modes which the pi does not have (it is also more expensive). – goldilocks Jan 23 '16 at 12:28
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    @goldilocks Shutting down the USB hub and LAN seems to have the most effect, slashing around 150mA (measured with reasonably accurate ammeter a minute ago) – Gene Dela Rosa Jan 23 '16 at 16:44
  • Point taken! I kinda skimmed over that. – goldilocks Jan 23 '16 at 16:47
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I have seen no other post which mentioned recompiling the Raspberry Pi Linux kernel for low energy usage.

I have no idea where any energy savings could be made.

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