Re: [RFC PATCH 1/1] fair.c: Add/Export find_idlest_perfer_cpu API

On Fri, 2012-08-17 at 12:46 -0700, Shirley Ma wrote:

Add/Export a new API for per-cpu thread model networking device driver
to choose a preferred idlest cpu within allowed cpumask.

The receiving CPUs of a networking device are not under cgroup controls.
Normally the receiving work will be scheduled on the cpu on which the
interrupts are received. When such a networking device uses per-cpu
thread model, the cpu which is chose to process the packets might not be
part of cgroup cpusets without using such an API here. 

On NUMA system, by using the preferred cpumask from the same NUMA node
would help to reduce expensive cross memory access to/from the other
NUMA node.

KVM per-cpu vhost will be the first one to use this API. Any other
device driver which uses per-cpu thread model and has cgroup cpuset
control will use this API later.

How often will this be called and how do you obtain the cpumasks
provided to the function?