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Date: Thu, 18 Dec 2014 10:22:27 +0800
From: Lai Jiangshan <laijs@...fujitsu.com>
To: Lai Jiangshan <laijs@...fujitsu.com>
CC: <linux-kernel@...r.kernel.org>, Tejun Heo <tj@...nel.org>,
Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
"Gu, Zheng" <guz.fnst@...fujitsu.com>,
tangchen <tangchen@...fujitsu.com>,
Hiroyuki KAMEZAWA <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH 2/5] workqueue: update wq_numa_possible_cpumask
On 12/12/2014 06:19 PM, Lai Jiangshan wrote:
> Yasuaki Ishimatsu hit a allocation failure bug when the numa mapping
> between CPU and node is changed. This was the last scene:
> 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
>
> Yasuaki Ishimatsu investigated that it happened in the following situation:
>
> 1) System Node/CPU before offline/online:
> | CPU
> ------------------------
> node 0 | 0-14, 60-74
> node 1 | 15-29, 75-89
> node 2 | 30-44, 90-104
> node 3 | 45-59, 105-119
>
> 2) A system-board (contains node2 and node3) is offline:
> | CPU
> ------------------------
> node 0 | 0-14, 60-74
> node 1 | 15-29, 75-89
>
> 3) A new system-board is online, two new node IDs are allocated
> for the two node of the SB, but the old CPU IDs are allocated for
> the SB, here the NUMA mapping between node and CPU is changed.
> (the node of CPU#30 is changed from node#2 to node#4, for example)
> | CPU
> ------------------------
> node 0 | 0-14, 60-74
> node 1 | 15-29, 75-89
> node 4 | 30-59
> node 5 | 90-119
>
> 4) now, the NUMA mapping is changed, but wq_numa_possible_cpumask
> which is the convenient NUMA mapping cache in workqueue.c is still outdated.
> thus pool->node calculated by get_unbound_pool() is incorrect.
>
> 5) when the create_worker() is called with the incorrect offlined
> pool->node, it is failed and the pool can't make any progress.
>
> To fix this bug, we need to fixup the wq_numa_possible_cpumask and the
> pool->node, the fix is so complicated that we split it into two patches,
> this patch fix the wq_numa_possible_cpumask and the next fix the pool->node.
>
> To fix the wq_numa_possible_cpumask, we only update the cpumasks of
> the orig_node and the new_node of the onlining @cpu. we con't touch
> other unrelated nodes since the wq subsystem haven't seen the changed.
>
> After this fix the new pool->node of new pools are correct.
> and existing wq's affinity is fixed up by wq_update_unbound_numa()
> after wq_update_numa_mapping().
>
> Reported-by: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
> Cc: Tejun Heo <tj@...nel.org>
> Cc: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
> Cc: "Gu, Zheng" <guz.fnst@...fujitsu.com>
> Cc: tangchen <tangchen@...fujitsu.com>
> Cc: Hiroyuki KAMEZAWA <kamezawa.hiroyu@...fujitsu.com>
> Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>
> ---
> kernel/workqueue.c | 42 +++++++++++++++++++++++++++++++++++++++++-
> 1 files changed, 41 insertions(+), 1 deletions(-)
>
> diff --git a/kernel/workqueue.c b/kernel/workqueue.c
> index a6fd2b8..4c88b61 100644
> --- a/kernel/workqueue.c
> +++ b/kernel/workqueue.c
> @@ -266,7 +266,7 @@ struct workqueue_struct {
> static struct kmem_cache *pwq_cache;
>
> static cpumask_var_t *wq_numa_possible_cpumask;
> - /* possible CPUs of each node */
> + /* PL: possible CPUs of each node */
>
> static bool wq_disable_numa;
> module_param_named(disable_numa, wq_disable_numa, bool, 0444);
> @@ -3949,6 +3949,44 @@ out_unlock:
> put_pwq_unlocked(old_pwq);
> }
>
> +static void wq_update_numa_mapping(int cpu)
> +{
> + int node, orig_node = NUMA_NO_NODE, new_node = cpu_to_node(cpu);
> +
> + lockdep_assert_held(&wq_pool_mutex);
> +
> + if (!wq_numa_enabled)
> + return;
> +
> + /* the node of onlining CPU is not NUMA_NO_NODE */
> + if (WARN_ON(new_node == NUMA_NO_NODE))
> + return;
> +
> + /* test whether the NUMA node mapping is changed. */
> + if (cpumask_test_cpu(cpu, wq_numa_possible_cpumask[new_node]))
> + return;
> +
> + /* find the origin node */
> + for_each_node(node) {
> + if (cpumask_test_cpu(cpu, wq_numa_possible_cpumask[node])) {
> + orig_node = node;
> + break;
> + }
> + }
> +
> + /* there may be multi mappings changed, re-initial. */
> + cpumask_clear(wq_numa_possible_cpumask[new_node]);
> + if (orig_node != NUMA_NO_NODE)
> + cpumask_clear(wq_numa_possible_cpumask[orig_node]);
> + for_each_possible_cpu(cpu) {
> + node = cpu_to_node(node);
Hi, Yasuaki Ishimatsu
The bug is here. It should be
node = cpu_to_node(cpu);
> + if (node == new_node)
> + cpumask_set_cpu(cpu, wq_numa_possible_cpumask[new_node]);
> + else if (orig_node != NUMA_NO_NODE && node == orig_node)
> + cpumask_set_cpu(cpu, wq_numa_possible_cpumask[orig_node]);
> + }
> +}
> +
> static int alloc_and_link_pwqs(struct workqueue_struct *wq)
> {
> bool highpri = wq->flags & WQ_HIGHPRI;
> @@ -4584,6 +4622,8 @@ static int workqueue_cpu_up_callback(struct notifier_block *nfb,
> mutex_unlock(&pool->attach_mutex);
> }
>
> + wq_update_numa_mapping(cpu);
> +
> /* update NUMA affinity of unbound workqueues */
> list_for_each_entry(wq, &workqueues, list)
> wq_update_unbound_numa(wq, cpu, true);
--
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