Source code

  • big.LITTLE MP

  • Maintained by Viresh Kumar <viresh.kumar at>


Purpose of this tree is to keep all ongoing efforts, which affect power management on big LITTLE systems, together at a single place. All of these must be targeted to get included in Mainline by their original authors.

There are three categories of branches that are kept here. One that are guaranteed to work on current big LITTLE system (Tested on ARM Vexpress TC2), ones which are experimental and ones which are being sent upstream and are under review. Branches can be moved from experimental or upstream to master, once we are convinced they don't break any existing stuff in master branch.

So, following is the category of Merge branches and topic branches we have:

Topic branches:

  • topic: We will track each of the topics in separate topic branches. They will be rebased over latest rc release from Linus
  • topic branches that are merged to make master branch are prefixed with "master-"
  • topic branches that are merged to make upstream branch are prefixed with "upstream-"

Merge branches:

  • big-LITTLE-MP-master-v*: Guaranteed to work on current big LITTLE system, ARM Vexpress TC2. This will be pulled in linux-linaro-tracking git tree.
  • big-LITTLE-MP-upstream-v*: Merge of all work sent upstream and is under review. Not to be pulled in linux-linaro-tracking git tree.

Branch refresh policy and pull requests

A new big-LITTLE-MP-master[upstream]-v* branch will be created for any new work or fixes that has been reported. Pull request for linux-linaro-tracking git tree will be sent twice in a release cycle.

  • On Monday two weeks before Kernel WG Freeze week (04-March-2013)
  • Friday before Kernel WG Freeze week (15-March-2013)

Topics being tracked in Master merge branch

task placement v2[-sysfs] (Morten Rasmussen)

Task placement [and sysfs support] for heterogeneous systems. This helps scheduler to decide on which cpu it must put a task on, based on its characteristics and cpu capacity.


arm multi pmu v2(Sudeep and Will Deacon)

ARM PMU support for Heteregeneous ARM platform


hw breakpoint fix (Lokesh Vutla)

Fix for hw breakpoint patch upstreamed by Dietmar

config fragments (Viresh Kumar)

Config fragments for big LITTLE MP scheduling.


Misc patches

Miscellaneous patches that might be useful for big LITTLE systems or its development

Topics being tracked in Upstream merge branch

sched-pack-small-tasks-v3.1-fixed(Vincent Guittot)

This packs the small tasks in as few as possible CPU/Cluster/Core. The main goal of packing small tasks is to reduce the power consumption by minimizing the number of power domain that are used.


DONT-UPSTREAM-arm-sched-tune-sched-domain-v1(Vincent Guittot)

Wouldn't be upstreamed.

sched-fix-env-src-active-migration-v1(Vincent Guittot)

sched-fix-nr_busy_cpus-v4.1(Vincent Guittot)

sched-fix-rq-load-with-rt-task-v2.1(Vincent Guittot)

sched-force-migration-on-cpu-w-capacity-v1(Vincent Guittot)

sched-use-LB_MIN-feature-v1(Vincent Guittot)

Other Topics being tracked

per-entity-load-tracking-with-core-sched-v2 (Preeti U Murthy)

This patchset is an attempt to begin the integration of PJT's metric with the load balancer in a step wise fashion,and progress based on the consequences.This patchset has been tested with the config excluding CONFIG_FAIR_GROUP_SCHED.


sched-timer-wq-migration-v2-resend (Viresh Kumar)

This enables scheduling workqueue on non-idle cpus and migrating running timers (timer that re-arms itself) to other cpus.


power-aware-scheduling-v5 (Alex Shi)

This adds power saving consideration in CFS scheduler. This was rebased on tip/master instead of any rc, and so isn't included in any merge.


runnable-load-avg-in-load-balance-v2 (Alex Shi)

use runnable load avg in cfs balance instead of instant load.


NO HZ (Frederic Weisbecker)

Required to port this for ARM. To be done by Kevin Hilman.


WorkingGroups/PowerManagement/Process/bigLittleMPTree (last modified 2013-03-14 05:19:24)