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Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and `mem_cgroup_shrink_node`

From Michal Hocko <mhocko@kernel.org>
Newsgroups linux.kernel
Subject Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and `mem_cgroup_shrink_node`
Date 2016-11-30 12:20 +0100
Message-ID <sJb5D-5oB-7@gated-at.bofh.it> (permalink)
References (5 earlier) <sGZii-1lC-27@gated-at.bofh.it> <sI3MR-2o2-3@gated-at.bofh.it> <sIrYT-1kN-65@gated-at.bofh.it> <sIteh-22H-15@gated-at.bofh.it> <sJajf-4SL-21@gated-at.bofh.it>
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[CCing Paul]

On Wed 30-11-16 11:28:34, Donald Buczek wrote:
[...]
> shrink_active_list gets and releases the spinlock and calls cond_resched().
> This should give other tasks a chance to run. Just as an experiment, I'm
> trying
> 
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1921,7 +1921,7 @@ static void shrink_active_list(unsigned long
> nr_to_scan,
>         spin_unlock_irq(&pgdat->lru_lock);
> 
>         while (!list_empty(&l_hold)) {
> -               cond_resched();
> +               cond_resched_rcu_qs();
>                 page = lru_to_page(&l_hold);
>                 list_del(&page->lru);
> 
> and didn't hit a rcu_sched warning for >21 hours uptime now. We'll see.

This is really interesting! Is it possible that the RCU stall detector
is somehow confused?

> Is preemption disabled for another reason?

I do not think so. I will have to double check the code but this is a
standard sleepable context. Just wondering what is the PREEMPT
configuration here?
-- 
Michal Hocko
SUSE Labs

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Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and  `mem_cgroup_shrink_node` Donald Buczek <buczek@molgen.mpg.de> - 2016-11-27 10:20 +0100
  Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and  `mem_cgroup_shrink_node` Michal Hocko <mhocko@kernel.org> - 2016-11-28 12:10 +0100
    Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and  `mem_cgroup_shrink_node` Paul Menzel <pmenzel@molgen.mpg.de> - 2016-11-28 13:30 +0100
      Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and  `mem_cgroup_shrink_node` Donald Buczek <buczek@molgen.mpg.de> - 2016-11-30 11:30 +0100
        Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and  `mem_cgroup_shrink_node` Michal Hocko <mhocko@kernel.org> - 2016-11-30 12:20 +0100
          Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and  `mem_cgroup_shrink_node` Donald Buczek <buczek@molgen.mpg.de> - 2016-11-30 12:50 +0100
            Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and  `mem_cgroup_shrink_node` Donald Buczek <buczek@molgen.mpg.de> - 2016-12-02 10:20 +0100
              Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and  `mem_cgroup_shrink_node` Donald Buczek <buczek@molgen.mpg.de> - 2016-12-06 09:40 +0100
          Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and  `mem_cgroup_shrink_node` "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-11-30 13:00 +0100
            Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and  `mem_cgroup_shrink_node` Paul Menzel <pmenzel@molgen.mpg.de> - 2016-11-30 13:40 +0100
              Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and  `mem_cgroup_shrink_node` "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-11-30 15:40 +0100
          Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and  `mem_cgroup_shrink_node` "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-11-30 13:00 +0100
            Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and  `mem_cgroup_shrink_node` Michal Hocko <mhocko@kernel.org> - 2016-11-30 14:20 +0100
              Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and  `mem_cgroup_shrink_node` "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-11-30 15:40 +0100
                Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and  `mem_cgroup_shrink_node` Peter Zijlstra <peterz@infradead.org> - 2016-11-30 17:40 +0100
                Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and  `mem_cgroup_shrink_node` Michal Hocko <mhocko@kernel.org> - 2016-11-30 18:10 +0100
                Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and  `mem_cgroup_shrink_node` "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-11-30 18:30 +0100
                Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and  `mem_cgroup_shrink_node` Michal Hocko <mhocko@kernel.org> - 2016-11-30 18:40 +0100
                Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and  `mem_cgroup_shrink_node` Peter Zijlstra <peterz@infradead.org> - 2016-11-30 19:00 +0100
                Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and  `mem_cgroup_shrink_node` "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-11-30 22:40 +0100
                Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and  `mem_cgroup_shrink_node` Peter Zijlstra <peterz@infradead.org> - 2016-12-01 06:40 +0100
                Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and  `mem_cgroup_shrink_node` "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-12-01 13:50 +0100
                Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and  `mem_cgroup_shrink_node` Peter Zijlstra <peterz@infradead.org> - 2016-12-01 17:40 +0100
                Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and  `mem_cgroup_shrink_node` "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-12-01 18:00 +0100
                Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and  `mem_cgroup_shrink_node` Peter Zijlstra <peterz@infradead.org> - 2016-12-01 19:20 +0100
                Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and  `mem_cgroup_shrink_node` "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-12-01 19:50 +0100
                Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and  `mem_cgroup_shrink_node` Peter Zijlstra <peterz@infradead.org> - 2016-12-01 20:00 +0100
                Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and  `mem_cgroup_shrink_node` "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-11-30 18:10 +0100

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