On Thu, Jul 04, 2013 at 06:37:19PM +0530, Srikar Dronamraju wrote:
> > static void task_numa_placement(struct task_struct *p)
> > {
> > int seq, nid, max_nid = 0;
> > @@ -897,7 +924,7 @@ static void task_numa_placement(struct task_struct *p)
> >
> > /* Find maximum private faults */
> > faults = p->numa_faults[task_faults_idx(nid, 1)];
> > - if (faults > max_faults) {
> > + if (faults > max_faults && !sched_numa_overloaded(nid)) {
>
> Should we take the other approach of setting the preferred nid but not
> moving the task to the node?
>
Why would that be better?
> So if some task moves out of the preferred node, then we should still be
> able to move this task there.
>
I think if we were to do that then I'd revisit the "task swap" logic from
autonuma (numacore had something similar) and search for pairs of tasks
that both benefit from a swap. I prototyped something basic alont this
lines but it was premature. It's a more directed approach but one that
should be done only when the private/shared and load logic is solidified.
> However your current approach has an advantage that it atleast runs on
> second preferred choice if not the first.
>
That was the intention.
> Also should sched_numa_overloaded() also consider pinned tasks?
>
I don't think sched_numa_overloaded() needs to as such, least I don't see how
it would do it sensibly right now. However, you still make an important point
in that find_idlest_cpu_node should take it into account. How about this?
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 9247345..387f28d 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -863,9 +863,13 @@ find_idlest_cpu_node(int this_cpu, int nid)
load = weighted_cpuload(i);
if (load < min_load) {
- /* Do not preempt a task running on a preferred node */
+ /*
+ * Do not preempt a task running on a preferred node or
+ * tasks are are pinned to their current CPU
+ */
struct task_struct *p = cpu_rq(i)->curr;
- if (p->numa_preferred_nid != nid) {
+ if (p->numa_preferred_nid != nid &&
+ cpumask_weight(tsk_cpus_allowed(p)) > 1) {
min_load = load;
idlest_cpu = i;
}
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