linux-kernel - Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and `mem_cgroup_shrink

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Date:   Fri, 2 Dec 2016 19:39:24 +0300
From:   Boris Zhmurov <bb@...nelpanic.ru>
To:     paulmck@...ux.vnet.ibm.com
Cc:     Michal Hocko <mhocko@...nel.org>,
        Paul Menzel <pmenzel@...gen.mpg.de>,
        Donald Buczek <buczek@...gen.mpg.de>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and
 `mem_cgroup_shrink_node`

Paul E. McKenney Thu Dec 01 2016 - 14:39:21 EST:

>> 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.

> Nice! Just to double-check, could you please also test your patch
> above with these two commits from -rcu?
> 
> d2db185bfee8 ("rcu: Remove short-term CPU kicking") f8f127e738e3
> ("rcu: Add long-term CPU kicking")
> 
> Thanx, Paul


Looks like patches d2db185bfee8 and f8f127e738e3 change nothing.

With cond_resched() in shrink_node_memcg and these two patches dmesg is
clean. No any RCU CPU stall messages.

Thanks.

-- 
Boris Zhmurov
mailto: bb@...nelpanic.ru
"wget http://kernelpanic.ru/bb_public_key.pgp -O - | gpg --import"