Re: [PATCH 2/4] workqueue: update per-cpu workqueue's node affinity at,online-offline

[Kamezawa Hiroyuki]

(2014/12/16 14:32), Lai Jiangshan wrote:
> On 12/15/2014 07:16 PM, Kamezawa Hiroyuki wrote:
> > The percpu workqueue pool are persistend and never be freed.
> > But cpu<->node relationship can be changed by cpu hotplug and pool->node
> > can point to an offlined node.
> >
> > If pool->node points to an offlined node,
> > following allocation failure can happen.
> >      ==
> >       SLUB: Unable to allocate memory on node 2 (gfp=0x80d0)
> >        cache: kmalloc-192, object size: 192, buffer size: 192, default
> > order:
> >      1, min order: 0
> >        node 0: slabs: 6172, objs: 259224, free: 245741
> >        node 1: slabs: 3261, objs: 136962, free: 127656
> >      ==
> >
> > This patch clears per-cpu workqueue pool's node affinity at
> > cpu offlining and restore it at cpu onlining.
> >
> > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> > ---
> >   kernel/workqueue.c | 11 ++++++++++-
> >   1 file changed, 10 insertions(+), 1 deletion(-)
> >
> > diff --git a/kernel/workqueue.c b/kernel/workqueue.c
> > index 7809154..2fd0bd7 100644
> > --- a/kernel/workqueue.c
> > +++ b/kernel/workqueue.c
> > @@ -4586,6 +4586,11 @@ static int workqueue_cpu_up_callback(struct notifier_block *nfb,
> >   	case CPU_DOWN_FAILED:
> >   	case CPU_ONLINE:
> >   		mutex_lock(&wq_pool_mutex);
> > +		/*
> > +		 * now cpu <-> node info is established. update numa node
> > +		 */
> > +		for_each_cpu_worker_pool(pool, cpu)
> > +			pool->node = cpu_to_node(cpu);
> >
> >   		for_each_pool(pool, pi) {
> >   			mutex_lock(&pool->attach_mutex);
> > @@ -4619,6 +4624,7 @@ static int workqueue_cpu_down_callback(struct notifier_block *nfb,
> >   	int cpu = (unsigned long)hcpu;
> >   	struct work_struct unbind_work;
> >   	struct workqueue_struct *wq;
> > +	struct worker_pool *pool;
> >
> >   	switch (action & ~CPU_TASKS_FROZEN) {
> >   	case CPU_DOWN_PREPARE:
> > @@ -4626,10 +4632,13 @@ static int workqueue_cpu_down_callback(struct notifier_block *nfb,
> >   		INIT_WORK_ONSTACK(&unbind_work, wq_unbind_fn);
> >   		queue_work_on(cpu, system_highpri_wq, &unbind_work);
> >
> > -		/* update NUMA affinity of unbound workqueues */
> >   		mutex_lock(&wq_pool_mutex);
> > +		/* update NUMA affinity of unbound workqueues */
> >   		list_for_each_entry(wq, &workqueues, list)
> >   			wq_update_unbound_numa(wq, cpu, false);
> > +		/* clear per-cpu workqueues's numa affinity. */
> > +		for_each_cpu_worker_pool(pool, cpu)
> > +			pool->node = NUMA_NO_NODE; /* restored at online */
>
>
> If the node is still online, it is better to keep the original pool->node.

Hm, ok, drop this code.  or moving all to node online event handler.

Thanks,
-Kame


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