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eMMC

The eMMC (embedded MMC) architecture puts the MMC components (flash memory plus controller) into a small ball grid array (BGA) IC package for use in circuit boards as an embedded non-volatile memory system. eMMC doesn't support the SPI-bus protocol.

Almost all mobile phones and tablets use this form of flash for main storage. The latest version of the eMMC standard (JESD84-B501) by JEDEC is version 5.01, with speeds rivaling discrete SATA based SSDs (400 MB/s).

#! /bin/sh

### BEGIN INIT INFO

# Provides:          ondemand

# Required-Start:    $remote_fs $all

# Required-Stop:

# Default-Start:     2 3 4 5

# Default-Stop:

# Short-Description: Set the CPU Frequency Scaling governor to "ondemand"

### END INIT INFO

PATH=/sbin:/usr/sbin:/bin:/usr/bin

. /lib/init/vars.sh

. /lib/lsb/init-functions

case "$1" in

    start)

        start-stop-daemon --start --background --exec /etc/init.d/ondemand -- background

        ;;

    background)

        sleep 60 # probably enough time for desktop login

        for CPUFREQ in /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor

        do

                [ -f $CPUFREQ ] || continue

                echo -n ondemand > $CPUFREQ

        done

        ;;

    restart|reload|force-reload)

        echo "Error: argument '$1' not supported" >&2

        exit 3

        ;;

    stop)

        ;;

    *)

        echo "Usage: $0 start|stop" >&2

        exit 3

        ;;

esac 

$ ls -al /sys/devices/system/cpu/cpu*/cpufreq/

/sys/devices/system/cpu/cpu0/cpufreq/:

합계 0

drwxr-xr-x 4 root root    0 2015-02-12 17:34 .

drwxr-xr-x 7 root root    0 2015-02-12 17:32 ..

-r--r--r-- 1 root root 4096 2015-02-12 17:43 affected_cpus

-r-------- 1 root root 4096 2015-02-12 17:43 cpuinfo_cur_freq

-r--r--r-- 1 root root 4096 2015-02-12 17:33 cpuinfo_max_freq

-r--r--r-- 1 root root 4096 2015-02-12 17:43 cpuinfo_min_freq

-r--r--r-- 1 root root 4096 2015-02-12 17:43 cpuinfo_transition_latency

drwxr-xr-x 2 root root    0 2015-02-12 17:43 ondemand

-r--r--r-- 1 root root 4096 2015-02-12 17:43 related_cpus

-r--r--r-- 1 root root 4096 2015-02-12 17:33 scaling_available_frequencies

-r--r--r-- 1 root root 4096 2015-02-12 17:43 scaling_available_governors

-r--r--r-- 1 root root 4096 2015-02-12 17:34 scaling_cur_freq

-r--r--r-- 1 root root 4096 2015-02-12 17:43 scaling_driver

-rw-r--r-- 1 root root 4096 2015-02-12 17:34 scaling_governor

-rw-r--r-- 1 root root 4096 2015-02-12 17:33 scaling_max_freq

-rw-r--r-- 1 root root 4096 2015-02-12 17:43 scaling_min_freq

-rw-r--r-- 1 root root 4096 2015-02-12 17:43 scaling_setspeed

drwxr-xr-x 2 root root    0 2015-02-12 17:43 stats 

$ cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_available_governors

conservative ondemand userspace powersave performance