tree 309546c03f1376d385e7cbf572c895e66d31e224
parent 9a871ed439f6c115ff5488e5e8287c39a7b5abc6
author Patrick Bellasi <patrick.bellasi@arm.com> 1436279600 +0100
committer Dmitry Shmidt <dimitrysh@google.com> 1485888398 -0800

ANDROID: sched/{fair,tune}: track RUNNABLE tasks impact on per CPU boost value

When per-task boosting is enabled, every time a task enters/exits a CPU
its boost value could impact the currently selected OPP for that CPU.
Thus, the "aggregated" boost value for that CPU potentially needs to
be updated to match the current maximum boost value among all the tasks
currently RUNNABLE on that CPU.

This patch introduces the required support to keep track of which boost
groups are impacting a CPU. Each time a task is enqueued/dequeued to/from
a CPU its boost group is used to increment a per-cpu counter of RUNNABLE
tasks on that CPU.
Only when the number of runnable tasks for a specific boost group
becomes 1 or 0 the corresponding boost group changes its effects on
that CPU, specifically:
  a) boost_group::tasks == 1: this boost group starts to impact the CPU
  b) boost_group::tasks == 0: this boost group stops to impact the CPU
In each of these two conditions the aggregation function:
  sched_cpu_update(cpu)
could be required to run in order to identify the new maximum boost
value required for the CPU.

The proposed patch minimizes the number of times the aggregation
function is executed while still providing the required support to
always boost a CPU to the maximum boost value required by all its
currently RUNNABLE tasks.

cc: Ingo Molnar <mingo@redhat.com>
cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com>
Signed-off-by: Andres Oportus <andresoportus@google.com>