Messages in this thread | | | Subject | Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and `mem_cgroup_shrink_node` | From | Donald Buczek <> | Date | Tue, 6 Dec 2016 09:32:01 +0100 |
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On 12/02/16 10:14, Donald Buczek wrote: > On 11/30/16 12:43, Donald Buczek wrote: >> On 11/30/16 12:09, Michal Hocko wrote: >>> [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? >> >> Wait... 21 hours is not yet a test result. > > For the records: We didn't have any stall warnings after 2 days and 20 > hours now and so I'm quite confident, that my above patch fixed the > problem for v4.8.0. On previous boots the rcu warnings started after > 37,0.2,1,2,0.8 hours uptime. > > Now I've applied this patch to stable latest (v4.8.11) on another > backup machine which suffered even more rcu stalls. > > Donald > >> [...]
For the records: After 3 days and 21 hours we've got a rcu stall warning again [1]. So my patch didn't fix it.
Trying "[PATCH] mm, vmscan: add cond_resched into shrink_node_memcg" from Michal Hocko [2] on top of v4.8.12 on both servers now.
[1] https://owww.molgen.mpg.de/~buczek/321322/2016-12-06.dmesg.txt [2] https://marc.info/?i=20161202095841.16648-1-mhocko%40kernel.org
-- Donald Buczek buczek@molgen.mpg.de Tel: +49 30 8413 1433
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