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

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Message-Id: <20161202164408.GM3924@linux.vnet.ibm.com>
Date:   Fri, 2 Dec 2016 08:44:08 -0800
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     Boris Zhmurov <bb@...nelpanic.ru>
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`

On Fri, Dec 02, 2016 at 07:39:24PM +0300, Boris Zhmurov wrote:
> 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.

Very good!  I have these two patches queued for 4.11.

And thank you again for all the testing!!!

							Thanx, Paul