From: Nikolay Borisov Subject: Re: Lockup in wait_transaction_locked under memory pressure Date: Mon, 29 Jun 2015 13:21:25 +0300 Message-ID: <55911C25.9090700@kyup.com> References: <20150625133138.GH14324@thunk.org> <558C06F7.9050406@kyup.com> <20150625140510.GI17237@dhcp22.suse.cz> <558C116E.2070204@kyup.com> <20150625151842.GK17237@dhcp22.suse.cz> <558C1DCE.1010705@kyup.com> <20150629083243.GB28471@dhcp22.suse.cz> <55910AEA.2030205@kyup.com> <20150629091629.GC28471@dhcp22.suse.cz> <55910E84.3000106@kyup.com> <20150629093826.GE28471@dhcp22.suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Cc: Theodore Ts'o , linux-ext4@vger.kernel.org, Marian Marinov To: Michal Hocko Return-path: Received: from mail.siteground.com ([67.19.240.234]:57869 "EHLO mail.siteground.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750809AbbF2KV3 (ORCPT ); Mon, 29 Jun 2015 06:21:29 -0400 In-Reply-To: <20150629093826.GE28471@dhcp22.suse.cz> Sender: linux-ext4-owner@vger.kernel.org List-ID: On 06/29/2015 12:38 PM, Michal Hocko wrote: > On Mon 29-06-15 12:23:16, Nikolay Borisov wrote: >> >> >> On 06/29/2015 12:16 PM, Michal Hocko wrote: >>> On Mon 29-06-15 12:07:54, Nikolay Borisov wrote: >>>> >>>> >>>> On 06/29/2015 11:32 AM, Michal Hocko wrote: >>>>> On Thu 25-06-15 18:27:10, Nikolay Borisov wrote: >>>>>> >>>>>> >>>>>> On 06/25/2015 06:18 PM, Michal Hocko wrote: >>>>>>> On Thu 25-06-15 17:34:22, Nikolay Borisov wrote: >>>>>>>> On 06/25/2015 05:05 PM, Michal Hocko wrote: >>>>>>>>> On Thu 25-06-15 16:49:43, Nikolay Borisov wrote: >>>>>>>>> [...] >>>>>>>>>> How would you advise to rectify such situation? >>>>>>>>> >>>>>>>>> As I've said. Check the oom victim traces and see if it is holding any >>>>>>>>> of those locks. >>>>>>>> >>>>>>>> As mentioned previously all OOM traces are identical to the one I've >>>>>>>> sent - OOM being called form the page fault path. >>>>>>> >>>>>>> By identical you mean that all of them kill the same task? Or just that >>>>>>> the path is same (which wouldn't be surprising as this is the only path >>>>>>> which triggers memcg oom killer)? >>>>>> >>>>>> The code path is the same, the tasks being killed are different >>>>> >>>>> Is the OOM killer triggered only for a singe memcg or others misbehave >>>>> as well? >>>> >>>> Generally OOM would be triggered for whichever memcg runs out of >>>> resources but so far I've only observed that the D state issue happens >>>> in a single containers. >>> >>> It is not clear whether it is the OOM memcg which has tasks in the D >>> state. Anyway I think it all smells like one memcg is throttling others >>> on another shared resource - journal in your case. >> >> Be that as it may, how do I find which cgroup is the culprit? > > Ted has already described that. You have to check all the running tasks > and try to find which of them is doing the operation which blocks > others. Transaction commit sounds like the first one to check. One other, fairly crucial detail - each and every container is on a separate block device, meaning the journals for different block devices is not being shared, since the journal is per-block device. I guess this means that whatever is happening is more or less constrained to the block device and thus the possibility that different memcg competing for the journal can be eliminated? >