Re: [PATCH 1/1] Add ARM cpu topology definition

Adding John Rigby here.

On 11 Jul 12, Amit Kucheria wrote:

From: Vincent Guittot vincent.guittot@linaro.org

(Patch accepted by Russell for 3.1: http://www.spinics.net/lists/arm-kernel/msg131273.html)

+config ARM_CPU_TOPOLOGY

• bool "Support cpu topology definition"
• depends on SMP && CPU_V7
• default y
• help

•  Support ARM cpu topology definition. The MPIDR register defines
  

•  affinity between processors which is then used to describe the cpu
  

•  topology of an ARM System.
  

+config SCHED_MC

• bool "Multi-core scheduler support"
• depends on ARM_CPU_TOPOLOGY
• help

•  Multi-core scheduler support improves the CPU scheduler's decision
  

•  making when dealing with multi-core CPU chips at a cost of slightly
  

•  increased overhead in some places. If unsure say N here.
  

+config SCHED_SMT

• bool "SMT scheduler support"
• depends on ARM_CPU_TOPOLOGY
• help

•  Improves the CPU scheduler's decision making when dealing with
  

•  MultiThreading at a cost of slightly increased overhead in some
  

•  places. If unsure say N here.
  

Can you please enable these Kconfig options in our configs? By default SCHED_MC/SMT expose a /sys interface and are disabled by default (0).

Possible values are:

0 - No power saving load balance (default value) 1 - Fill one thread/core/package first for long running threads 2 - Also bias task wakeups to semi-idle cpu package for power savings

See Documentation/ABI/testing/sysfs-devices-system-cpu for details.

This will make it easy to turn on for folks that are interested (by writing 2 to /sys/devices/system/cpu/sched_mc_power_savings)

Regards, Amit