回复: Question on io-wq

["Zhang, Qiang" <Qiang.Zhang@windriver.com>]

________________________________________
发件人: Zhang, Qiang <Qiang.Zhang@windriver.com>
发送时间: 2020年10月23日 11:55
收件人: Jens Axboe
抄送: viro@zeniv.linux.org.uk; io-uring@vger.kernel.org; linux-kernel@vger.kernel.org; linux-fsdevel@vger.kernel.org
主题: 回复: Question on io-wq



________________________________________
发件人: Jens Axboe <axboe@kernel.dk>
发送时间: 2020年10月22日 22:08
收件人: Zhang, Qiang
抄送: viro@zeniv.linux.org.uk; io-uring@vger.kernel.org; linux-kernel@vger.kernel.org; linux-fsdevel@vger.kernel.org
主题: Re: Question on io-wq

On 10/22/20 3:02 AM, Zhang,Qiang wrote:
>
> Hi Jens Axboe
>
> There are some problem in 'io_wqe_worker' thread, when the
> 'io_wqe_worker' be create and  Setting the affinity of CPUs in NUMA
> nodes, due to CPU hotplug, When the last CPU going down, the
> 'io_wqe_worker' thread will run anywhere. when the CPU in the node goes
> online again, we should restore their cpu bindings?

>Something like the below should help in ensuring affinities are
>always correct - trigger an affinity set for an online CPU event. We
>should not need to do it for offlining. Can you test it?


>diff --git a/fs/io-wq.c b/fs/io-wq.c
>index 4012ff541b7b..3bf029d1170e 100644
>--- a/fs/io-wq.c
>+++ b/fs/io-wq.c
>@@ -19,6 +19,7 @@
 >#include <linux/task_work.h>
 >#include <linux/blk-cgroup.h>
 >#include <linux/audit.h>
>+#include <linux/cpu.h>

 >#include "io-wq.h"
>
>@@ -123,9 +124,13 @@ struct io_wq {
 >       refcount_t refs;
  >      struct completion done;
>
>+       struct hlist_node cpuhp_node;
>+
 >       refcount_t use_refs;
 >};
>
>+static enum cpuhp_state io_wq_online;
>+
 >static bool io_worker_get(struct io_worker *worker)
 >{
   >     return refcount_inc_not_zero(&worker->ref);
>@@ -1096,6 +1101,13 @@ struct io_wq *io_wq_create(unsigned bounded, >struct io_wq_data *data)
 >               return ERR_PTR(-ENOMEM);
  >      }
>
>+       ret = cpuhp_state_add_instance_nocalls(io_wq_online, >&wq->cpuhp_node);
>+       if (ret) {
>+               kfree(wq->wqes);
>+               kfree(wq);
>+               return ERR_PTR(ret);
>+       }
>+
>        wq->free_work = data->free_work;
>        wq->do_work = data->do_work;
>
>@@ -1145,6 +1157,7 @@ struct io_wq *io_wq_create(unsigned bounded, >struct io_wq_data *data)
 >       ret = PTR_ERR(wq->manager);
 >       complete(&wq->done);
 >err:
>+       cpuhp_state_remove_instance_nocalls(io_wq_online, >&wq->cpuhp_node);
  >      for_each_node(node)
 >               kfree(wq->wqes[node]);
 >       kfree(wq->wqes);
>@@ -1164,6 +1177,8 @@ static void __io_wq_destroy(struct io_wq *wq)
 >{
 >       int node;
>
>+       cpuhp_state_remove_instance_nocalls(io_wq_online, >&wq->cpuhp_node);
>+
   >     set_bit(IO_WQ_BIT_EXIT, &wq->state);
  >      if (wq->manager)
 >               kthread_stop(wq->manager);
>@@ -1191,3 +1206,40 @@ struct task_struct *io_wq_get_task(struct io_wq >*wq)
 >{
 >      return wq->manager;
 >}
>+
>+static bool io_wq_worker_affinity(struct io_worker *worker, void *data)
>+{
>+       struct task_struct *task = worker->task;
>+       unsigned long flags;
>+
           struct rq_flags rf;
           struct rq *rq;
           rq = task_rq_lock(task, &rf);

---       raw_spin_lock_irqsave(&task->pi_lock, flags);
>+       do_set_cpus_allowed(task, cpumask_of_node(worker->wqe->node));
>+       task->flags |= PF_NO_SETAFFINITY;
---      raw_spin_unlock_irqrestore(&task->pi_lock, flags);
           
              task_rq_unlock(rq, task, &rf);

>+       return false;
>+}
>+
>+static int io_wq_cpu_online(unsigned int cpu, struct hlist_node *node)
>+{
>+       struct io_wq *wq = hlist_entry_safe(node, struct io_wq, cpuhp_node);
>+       int i;
>+
>+       rcu_read_lock();
>+       for_each_node(i)
>+               io_wq_for_each_worker(wq->wqes[i], io_wq_worker_affinity, >NULL);
>+       rcu_read_unlock();
>+       return 0;
>+}
>+
>+static __init int io_wq_init(void)
>+{
>+       int ret;
>+
>+       ret = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN, >"io->wq/online",
>+                                       io_wq_cpu_online, NULL);
>+       if (ret < 0)
>+               return ret;
>+       io_wq_online = ret;
>+       return 0;
>+}
>+subsys_initcall(io_wq_init);
>
>--
>Jens Axboe