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

[Peter Zijlstra <peterz@infradead.org>]

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?