sched: pack small tasks
Date	Fri, 22 Mar 2013 13:25:52 +0100

During the creation of sched_domain, we define a pack buddy CPU for each CPU
when one is available. We want to pack at all levels where a group of CPU can
be power gated independently from others.
On a system that can't power gate a group of CPUs independently, the flag is
set at all sched_domain level and the buddy is set to -1. This is the default
behavior.
On a dual clusters / dual cores system which can power gate each core and
cluster independently, the buddy configuration will be :

      | Cluster 0   | Cluster 1   |
      | CPU0 | CPU1 | CPU2 | CPU3 |
-----------------------------------
buddy | CPU0 | CPU0 | CPU0 | CPU2 |
Small tasks tend to slip out of the periodic load balance so the best place
to choose to migrate them is during their wake up. The decision is in O(1) as
we only check again one buddy CPU

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Morten Rasmussen <morten.rasmussen@arm.com>
sched: secure access to other CPU statistics
Date	Fri, 22 Mar 2013 13:25:53 +0100

If a CPU accesses the runnable_avg_sum and runnable_avg_period fields of its
buddy CPU while the latter updates it, it can get the new version of a field
and the old version of the other one. This can generate erroneous decisions.
We don't want to use a lock mechanism for ensuring the coherency because of
the overhead in this critical path. The previous attempt can't ensure
coherency of both fields for 100% of the platform and use case as it will
depend of the toolchain and the platform architecture.
The runnable_avg_period of a runqueue tends to the max value in less than
345ms after plugging a CPU, which implies that we could use the max value
instead of reading runnable_avg_period after 345ms. During the starting phase,
we must ensure a minimum of coherency between the fields. A simple rule is
runnable_avg_sum <= runnable_avg_period.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Morten Rasmussen <morten.rasmussen@arm.com>
sched: pack the idle load balance
Date	Fri, 22 Mar 2013 13:25:54 +0100

Look for an idle CPU close to the pack buddy CPU whenever possible.
The goal is to prevent the wake up of a CPU which doesn't share the power
domain of the pack buddy CPU.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Morten Rasmussen <morten.rasmussen@arm.com>
modified for Mako hybrid kernel

Signed-off-by: faux123 <reioux@gmail.com>
ARM: 7461/1: topology: Add arch_scale_freq_power function

Add infrastructure to be able to modify the cpu_power of each core

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
ARM: 7462/1: topology: factorize the update of sibling masks

This factorization has also been proposed in another patch that has not been
merged yet:
http://lists.infradead.org/pipermail/linux-arm-kernel/2012-January/080873.html
So, this patch could be dropped depending of the state of the other one.

Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
ARM: 7463/1: topology: Update cpu_power according to DT information

Use cpu compatibility field and clock-frequency field of DT to
estimate the capacity of each core of the system and to update
the cpu_power field accordingly.
This patch enables to put more running tasks on big cores than
on LITTLE ones. But this patch doesn't ensure that long running
tasks will run on big cores and short ones on LITTLE cores.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
ARM: 7482/1: topology: fix section mismatch warning for init_cpu_topology

Get rid of this warning..
arch/arm/kernel/built-in.o(.text+0xac78): Section mismatch in reference
from the function init_cpu_topology() to the function
 .init.text:parse_dt_topology()
The function init_cpu_topology() references
the function __init parse_dt_topology().
This is often because init_cpu_topology lacks a __init
annotation or the annotation of parse_dt_topology is wrong.

Signed-off-by: Venkatraman S <svenkatr@ti.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
ARM: kernel: enhance MPIDR macro definitions

Kernel subsystems other than the topology layer need the MPIDR
mask definitions to access the MPIDR without relying on hardcoded
masks. This patch moves the MPIDR register masks definition to
a header file and defines a macro to simplify access to MPIDR bit fields
representing affinity levels.

Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
ARM: kernel: update topology to use new MPIDR macros

This patch updates the topology initialization code to use the newly
defined accessors to retrieve the MPIDR affinity levels.

Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
ARM: (Experimental) Provide Estimated CPU Capacity measure

Bsed upon the CPU Power of a core, computes a capacity measure
between 0 and 1024 scaling in line with the frequency using a
simple linear scale derived from the maximum frequency reported
by CPUFreq.

Scaling CPU Power with frequency and estimated capacity gives an
estimate of the amount of potential compute capacity available to
a specific core relative to any other in the system.

Change-Id: I8048a23fe5999536b6325a5ec64549dd69f5a865
backported for Mako Hybrid kernel from LKML

Signed-off-by: Paul Reioux <reioux@gmail.com>
sched: introduce compute capacity for CPUs, groups and domains

Date	Tue, 16 Apr 2013 16:26:16 +0100

Using the per-cpu compute capacity exported from topology
when CONFIG_ARCH_SCALE_INVARIANT_CPU_CAPACITY is active, place this
information alongside cpu_power in the scheduler and combine for the
various aggregating entities.

Change-Id: I4984c335bcdc128680e7459b3f86bb05e04593cc
backported for Mako Hybrid from LKML

Signed-off-by: Paul Reioux <reioux@gmail.com>
sched: Scale load contribution by CPU Capacity

Date	Tue, 16 Apr 2013 16:26:35 +0100

Modulate the tracked load of a task using the measure of current
and maximum compute capacity for the core it is executing on.

Change-Id: If6aea806e631f2313fd925c8902260a522663dbd
backported for mako hybrid kernel from LKML

Signed-off-by: Paul Reioux <reioux@gmail.com>
Revert "sched: pack the idle load balance"

This reverts commit 53b48168e8a74b557a9fea0d87b6be6e7b506c7c.