On Thu, Jul 04, 2013 at 05:56:44PM +0530, Srikar Dronamraju wrote:
> * Mel Gorman <mgorman@xxxxxxx> [2013-07-03 15:21:33]:
>
> >
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index 2a0bbc2..b9139be 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -800,6 +800,37 @@ unsigned int sysctl_numa_balancing_scan_delay = 1000;
> > */
> > unsigned int sysctl_numa_balancing_settle_count __read_mostly = 3;
> >
> > +static unsigned long weighted_cpuload(const int cpu);
> > +
> > +static int
> > +find_idlest_cpu_node(int this_cpu, int nid)
> > +{
> > + unsigned long load, min_load = ULONG_MAX;
> > + int i, idlest_cpu = this_cpu;
> > +
> > + BUG_ON(cpu_to_node(this_cpu) == nid);
> > +
> > + for_each_cpu(i, cpumask_of_node(nid)) {
> > + load = weighted_cpuload(i);
> > +
> > + if (load < min_load) {
> > + struct task_struct *p;
> > +
> > + /* Do not preempt a task running on its preferred node */
> > + struct rq *rq = cpu_rq(i);
> > + raw_spin_lock_irq(&rq->lock);
>
> Not sure why we need this spin_lock? Cant this be done in a rcu block
> instead?
>
Judging by how find_idlest_cpu works it would appear you are correct.
Thanks very much, I'm still pretty much a scheduler wuss. I know what I
want but not always how to get it :)
--
Mel Gorman
SUSE Labs
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