[AT&T, Rogers HTC One X, Telstra One XL] Zarboz:
What is msm_mpdecision?

100% kernel based multi core decision! (should cpu1/2/3 be online or not?)

This replaces your /system/bin/mpdecision binary which is renamed by the installer to mpdecision_bck.

Check /sys/kernel/msm_mpdecision/conf/ for the configuration.

startdelay = time until mpdecision starts doing it's magic (20000)

delay = time between checks (70)

pause = if something else plugs in the cpu, fall asleep for 10000ms (10 secs)

scroff_single_core = if the screen is off, don't plug in cpu1/2/3. Additionally: Unplug all cpus except cpu0 when screen is turned off (1)

enabled = enable(1) or disable(0) mpdecision. This does not affect scroff_single_core!

min_cpus = min cpus to be online, cannot be < 1. Default: 1

max_cpus = max cpus to be online, cannot be > 4. (if you set it to 2 and min_cpus to 1 you will basically have a dualcore) Default: 4

idle_freq = a value against that will be checked if a core +/- is requested. (486000)

If cpu0 is below that value and a core up of another cpu is requested, nothing will happen.

If any other cpu is above that value and a core down of that cpu is requested, nothing will happen. (otherwise it would now put down that cpu even though it is still working, which isn't what we want)

Hot plug thresholds (aka now it gets 'complicated')

This small formula calculates which value will be used: (number_of_cpus_online - 1) * 2

The result of this formula will be the nwns_threshold where a new cpu is hotplugged.

The result of this formula + 1 will be the nwns_threshold where a cpu is unplugged.

nwns_threshold_x = runqueue threshold, if this is reached cpuX will be hot/unplugged

twts_threshold_x = time threshold, this amount of time must have passed for the related action to be taken (hot/unplug)

Example:

One cpu is online.

(1 - 1) * 2 = 0 ergo:

nwns_threshold_0 = cpu1 will be hotplugged at this value

((1 - 1) * 2) + 1 = 1

nwns_threshold_1 = cpu0 will be unplugged at this value

Since we can't unplug cpu0 this is '0'.

Two cpus are online.

(2 - 1) * 2 = 2 ergo:

nwns_threshold_2 = cpu2 will be hotplugged at this value

((2 - 1) * 2) + 1 = 3

nwns_threshold_3 = cpu1 will be unplugged at this value

etc...

The default values are:

NwNs_Threshold: 12, 0, 25, 20, 32, 28, 0, 35

TwTs_Threshold: 140, 0, 140, 190, 140, 190, 0, 190

Where the position and function of the number equals the result of the above explained formula.

(all times are in ms)

If you want to see the mpdecision magic happening:

adb shell
cat /proc/kmsg | grep 'MPDEC'

mpdecision's input event boost, aka project butter :p

This will boost your min cpu speed if you touch the screen or press a button and gives you full control.

In those events the min cpu freq will be risen to a predefined value (look below) on every online cpu. This boosts overall reaction times and smoothness a lot. (works similar to the qcom mpdecision binary)

Configuration files:

root@android:/sys/kernel/msm_mpdecision/conf # ls

boost_enabled

boost_freqs

boost_time

All of them work like the usual sysfs files, except one special case:

boost_freqs will list all frequencies from cpu 0 to cpu x. Cpu 3 and any following cpu will share one frequency.

To change those frequencies echo the cpu number + the frequency in khz. To change the boost freq of cpu3 (and 4,5,6,7,8, etc) the echo would look as follows:

echo "3 1026000" > /sys/kernel/msm_mpdecision/conf/boost_freqs

for cpu0:

echo "0 1026000" > /sys/kernel/msm_mpdecision/conf/boost_freqs

Defaults:

cat /sys/kernel/msm_mpdecision/conf/boost_freqs
918000
918000
702000
594000