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Subject[RFC][PATCH 15/26] sched, numa: Implement hotplug hooks
start/stop numa balance threads on-demand using cpu-hotlpug.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
kernel/sched/numa.c | 62 ++++++++++++++++++++++++++++++++++++++++++++++------
1 file changed, 55 insertions(+), 7 deletions(-)
--- a/kernel/sched/numa.c
+++ b/kernel/sched/numa.c
@@ -596,31 +596,79 @@ static int numad_thread(void *data)
return 0;
}

+static int __cpuinit
+numa_hotplug(struct notifier_block *nb, unsigned long action, void *hcpu)
+{
+ int cpu = (long)hcpu;
+ int node = cpu_to_node(cpu);
+ struct node_queue *nq = nq_of(node);
+ struct task_struct *numad;
+ int err = 0;
+
+ switch (action & ~CPU_TASKS_FROZEN) {
+ case CPU_UP_PREPARE:
+ if (nq->numad)
+ break;
+
+ numad = kthread_create_on_node(numad_thread,
+ nq, node, "numad/%d", node);
+ if (IS_ERR(numad)) {
+ err = PTR_ERR(numad);
+ break;
+ }
+
+ nq->numad = numad;
+ nq->next_schedule = jiffies + HZ; // XXX sync-up?
+ break;
+
+ case CPU_ONLINE:
+ wake_up_process(nq->numad);
+ break;
+
+ case CPU_DEAD:
+ case CPU_UP_CANCELED:
+ if (!nq->numad)
+ break;
+
+ if (cpumask_any_and(cpu_online_mask,
+ cpumask_of_node(node)) >= nr_cpu_ids) {
+ kthread_stop(nq->numad);
+ nq->numad = NULL;
+ }
+ break;
+ }
+
+ return notifier_from_errno(err);
+}
+
static __init int numa_init(void)
{
- int node;
+ int node, cpu, err;

nqs = kzalloc(sizeof(struct node_queue*) * nr_node_ids, GFP_KERNEL);
BUG_ON(!nqs);

- for_each_node(node) { // XXX hotplug
+ for_each_node(node) {
struct node_queue *nq = kmalloc_node(sizeof(*nq),
GFP_KERNEL | __GFP_ZERO, node);
BUG_ON(!nq);

- nq->numad = kthread_create_on_node(numad_thread,
- nq, node, "numad/%d", node);
- BUG_ON(IS_ERR(nq->numad));
-
spin_lock_init(&nq->lock);
INIT_LIST_HEAD(&nq->entity_list);

nq->next_schedule = jiffies + HZ;
nq->node = node;
nqs[node] = nq;
+ }

- wake_up_process(nq->numad);
+ get_online_cpus();
+ cpu_notifier(numa_hotplug, 0);
+ for_each_online_cpu(cpu) {
+ err = numa_hotplug(NULL, CPU_UP_PREPARE, (void *)(long)cpu);
+ BUG_ON(notifier_to_errno(err));
+ numa_hotplug(NULL, CPU_ONLINE, (void *)(long)cpu);
}
+ put_online_cpus();

return 0;
}



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