embeded/raspberry pi2018.04.17 15:29


Edit /boot/cmdline.txt and add maxcpus=N

[링크 : https://www.raspberrypi.org/forums/viewtopic.php?f=29&t=99372]

[링크 : https://www.raspberrypi.org/forums/viewtopic.php?t=152692]


USB 허브 끄기 - 단, 네트워크도 죽어버림(그럼 도대체 어떻게 쓰란거지 -ㅁ-?)

#!/bin/bash

#Code to stop

/etc/init.d/networking stop

echo 0 > /sys/devices/platform/bcm2708_usb/buspower;

echo “Bus power stopping”


#!/bin/bash

#Code to start

echo 1 > /sys/devices/platform/bcm2708_usb/buspower;

echo “Bus power starting”

sleep 2;

/etc/init.d/networking start 


video output 끄기

This tip has been suggested by many people. If your system is headless (no video output) you can turn off the HDMI port with:

sudo /opt/vc/bin/tvservice -o

to turn it back on:

sudo /opt/vc/bin/tvservice -p

This command will save you around 20-30mA. 

[링크 : https://babaawesam.com/2014/01/24/power-saving-tips-for-raspberry-pi/]


/sys/devices/system/cpu/cpu0/online 이 있으면 논리적으로 on/off 가능하다는데

라즈베리에는 

/sys/devices/system/cpu/online

/sys/devices/system/cpu/offline 만 존재한다.

[링크 : https://stackoverflow.com/questions/44907731/programmatically-disable-cpu-core]


+

$ chcpu


Usage:

 chcpu [options]


Options:

  -h, --help                    print this help

  -e, --enable <cpu-list>       enable cpus

  -d, --disable <cpu-list>      disable cpus

  -c, --configure <cpu-list>    configure cpus

  -g, --deconfigure <cpu-list>  deconfigure cpus

  -p, --dispatch <mode>         set dispatching mode

  -r, --rescan                  trigger rescan of cpus

  -V, --version                 output version information and exit 


라즈베리에서는 안되네..

$ sudo chcpu -r

chcpu: This system does not support rescanning of CPUs

$ sudo chcpu -e 2

chcpu: CPU 2 is not hot pluggable 

[링크 : https://www.ibm.com/support/knowledgecenter/en/linuxonibm/com.ibm.linux.z.lgdd/lgdd_t_cpu_online.html]


+

/sys/devices/system/cpu/cpufreq/ondemand $ cat up_threshold

50 

[링크 : https://raspberrypi.stackexchange.com/questions/9034/how-to-change-the-default-governor]

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