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

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On Thu 01-12-16 21:10:01, Boris Zhmurov wrote:
> Michal Hocko 30/11/16 21:25:
> 
> >>> Do I get it right that s@cond_resched_rcu_qs@cond_resched@ didn't help?
> >>
> >> I didn't try that. I've tried 4 patches from Paul's linux-rcu tree.
> >> I can try another portion of patches, no problem :)
> > 
> > Replacing cond_resched_rcu_qs in shrink_node_memcg by cond_resched would
> > be really helpful to tell whether we are missing a real scheduling point
> > or whether something more serious is going on here.
> 
> Well, I can confirm, that replacing cond_resched_rcu_qs in
> shrink_node_memcg by cond_resched also makes dmesg clean from RCU CPU
> stall warnings.
> 
> I've attached patch (just modification of Paul's patch), that fixes RCU
> stall messages in situations, when all memory is used by
> couchbase/memcached + fs cache and linux starts to use swap.

OK, thanks for the confirmation! I will send a patch because it is true
that we do not have any scheduling point if no pages can be isolated
fromm the LRU. This might be what you are seeing.
-- 
Michal Hocko
SUSE Labs

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Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and  `mem_cgroup_shrink_node` Boris Zhmurov <bb@kernelpanic.ru> - 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 20:40 +0100
  Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and  `mem_cgroup_shrink_node` Michal Hocko <mhocko@kernel.org> - 2016-12-02 10:40 +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> - 2016-12-02 15:00 +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> - 2016-12-02 17:50 +0100
    Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and  `mem_cgroup_shrink_node` Michal Hocko <mhocko@kernel.org> - 2016-12-02 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> - 2016-12-02 18:20 +0100
  Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and  `mem_cgroup_shrink_node` Boris Zhmurov <bb@kernelpanic.ru> - 2016-12-02 17:50 +0100

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