Re: [PATCH 1/3] arm64: topology: Implement basic CPU topology support

On 2013-12-12 4:00, Mark Brown wrote:

From: Mark Brown broonie@linaro.org

Add basic CPU topology support to arm64, based on the existing pre-v8 code and some work done by Mark Hambleton. This patch does not implement any topology discovery support since that should be based on information from firmware, it merely implements the scaffolding for integration of topology support in the architecture.

The goal is to separate the architecture hookup for providing topology information from the DT parsing in order to ease review and avoid blocking the architecture code (which will be built on by other work) with the DT code review by providing something something simple and basic.

A following patch will implement support for parsing the DT topology bindings for ARM, similar patches will be needed for ACPI.

Signed-off-by: Mark Brown broonie@linaro.org

arch/arm64/Kconfig | 8 +++ arch/arm64/include/asm/topology.h | 42 +++++++++++++ arch/arm64/kernel/Makefile | 1 + arch/arm64/kernel/smp.c | 12 ++++ arch/arm64/kernel/topology.c | 124 ++++++++++++++++++++++++++++++++++++++ 5 files changed, 187 insertions(+) create mode 100644 arch/arm64/include/asm/topology.h create mode 100644 arch/arm64/kernel/topology.c

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 6d4dd22ee4b7..c0975fea9bfe 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -154,6 +154,14 @@ config SMP If you don't know what to do here, say N. +config ARM_CPU_TOPOLOGY

• bool "Support CPU topology definition"
• depends on SMP
• default y
• help

•  Support CPU topology definition, based on configuration
  

•  provided by the firmware.
  

The scheduler already used topology and cache sharing when CONFIG_SCHED_MC and/or CONFIG_SCHED_SMT are enable. can you add these configs for arm64 so the scheduler can use it? something like:

+config SCHED_MC + bool "Multi-core scheduler support" + depends on ARM64_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 ARM64_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. +

Thanks Hanjun