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

Kamezawa Hiroyuki
2014-12-16T07:26:10Z

(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@jp.fujitsu.com>
>> ---
>> 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