On Thu 01-12-16 21:10:01, Boris Zhmurov wrote:

Michal Hocko 30/11/16 21:25:

quoted

quoted

quoted

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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