Auto CPU Hotplug

Android was not made for embedded system. It was designed for Mobile phones. You will find many instances where things will not be working as expected, if you are working to make android work for embedded system.

One of the issue was this cpu killing each other to save battery.


<7>[ 154.890391] [rfkill]: rfkill set power 1
<5>[ 158.611398] CPU1: shutdown
<6>[ 158.611431] [hotplug]: cpu(0) try to kill cpu(1)
<6>[ 158.611495] [hotplug]: cpu1 is killed! .
<7>[ 161.110704] CPU1: Booted secondary processor
<7>[ 162.610842] CPU3: Booted secondary processor
<5>[ 163.611427] CPU1: shutdown
<6>[ 163.611454] [hotplug]: cpu(2) try to kill cpu(1)
<6>[ 163.612531] [hotplug]: cpu1 is killed! .

If you do


cat /sys/devices/system/cpu/offline

then you will see that some cores are killed not online

 


cat /sys/devices/system/cpu/online

Above will give you which cores are online at this moment.

 

I saw some process named auto_cpu_hotplu but I was not able to kill that process.

Fix was very simple though

echo 0 > /sys/kernel/autohotplug/enable

Done!!

For highest performance you can issue below commands also

 

echo performance > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor

echo 1 > /sys/devices/system/cpu/cpu0/online

echo performance > /sys/devices/system/cpu/cpu1/cpufreq/scaling_governor

echo 1 > /sys/devices/system/cpu/cpu1/online

echo 1 > /sys/devices/system/cpu/cpu2/online

echo 1 > /sys/devices/system/cpu/cpu3/online

 
Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s