big.LITTLE Support in Android at Linux Plumbers conference

[Tim Ansell]

Hi,

LWN had a write up on the Linux Plumbers Android microconference that was held in Seattle on August 20th at http://lwn.net/Articles/657139/

There was a talk by Todd Kjos & Tim Murray from Google about the "big.LITTLE Support in Android" that is interesting. The slides are below;

http://www.linuxplumbersconf.org/2015/ocw//system/presentations/3399/original/LPC-tkjos.pdf

One interesting slide says;

ActivityManager and cpusets 

* ActivityManager keeps track of foreground and background apps 

* Any app that is considered foreground gets put in foreground cpuset, similar for background

Tim 'mithro' Ansell

[Sami Kyostila]

Thanks for sharing. I wonder if that means that all threads of an app will always run on either on big or little cores but never a mix of both?

- Sami

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[Tim Ansell]

The slides explain;

cpusets in Android 

● Two cpusets set up at init: foreground and background 

● Foreground should contain all cores, background contains a small subset (generally one little core) 

● cpuset configuration is in device-specific init.rc files

Which seems to indicate that background stuff will only run on the little cores and foreground stuff will run on either.

Tim

[Yoshi]

Is the cpuset designed specially for android?

I found that there are only two files (/dev/cpuset/background & /dev/cpuset/foreground/) in Android M which is different from Vanilla's cpuset cgroup.

Yoshi