From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f69.google.com (mail-wm0-f69.google.com [74.125.82.69]) by kanga.kvack.org (Postfix) with ESMTP id 9FF336B0292 for ; Thu, 29 Jun 2017 13:46:40 -0400 (EDT) Received: by mail-wm0-f69.google.com with SMTP id l81so3383089wmg.8 for ; Thu, 29 Jun 2017 10:46:40 -0700 (PDT) Received: from mail-wm0-x229.google.com (mail-wm0-x229.google.com. [2a00:1450:400c:c09::229]) by mx.google.com with ESMTPS id p64si1717421wmd.165.2017.06.29.10.46.39 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 29 Jun 2017 10:46:39 -0700 (PDT) Received: by mail-wm0-x229.google.com with SMTP id 62so89390994wmw.1 for ; Thu, 29 Jun 2017 10:46:39 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20170627155035.GA20189@dhcp22.suse.cz> References: <20170627071104.GB28078@dhcp22.suse.cz> <20170627155035.GA20189@dhcp22.suse.cz> From: Luigi Semenzato Date: Thu, 29 Jun 2017 10:46:37 -0700 Message-ID: Subject: Re: OOM kills with lots of free swap Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Minchan Kim , Linux Memory Management List Well, my apologies, I haven't been able to reproduce the problem, so there's nothing to go on here. We had a bug (a local patch) which caused this, then I had a bug in my test case, so I was confused. I also have a recollection of this happening in older kernels (3.8 I think), but I am not going to go back that far since even if the problem exists, we have no evidence it happens frequently. Thanks! On Tue, Jun 27, 2017 at 8:50 AM, Michal Hocko wrote: > On Tue 27-06-17 08:22:36, Luigi Semenzato wrote: >> (sorry, I forgot to turn off HTML formatting) >> >> Thank you, I can try this on ToT, although I think that the problem is >> not with the OOM killer itself but earlier---i.e. invoking the OOM >> killer seems unnecessary and wrong. Here's the question. >> >> The general strategy for page allocation seems to be (please correct >> me as needed): >> >> 1. look in the free lists >> 2. if that did not succeed, try to reclaim, then try again to allocate >> 3. keep trying as long as progress is made (i.e. something was reclaimed) >> 4. if no progress was made and no pages were found, invoke the OOM killer. > > Yes that is the case very broadly speaking. The hard question really is > what "no progress" actually means. We use "no pages could be reclaimed" > as the indicator. We cannot blow up at the first such instance of > course because that could be too early (e.g. data under writeback > and many other details). With 4.7+ kernels this is implemented in > should_reclaim_retry. Prior to the rework we used to rely on > zone_reclaimable which simply checked how many pages we have scanned > since the last page has been freed and if that is 6 times the > reclaimable memory then we simply give up. It had some issues described > in 0a0337e0d1d1 ("mm, oom: rework oom detection"). > >> I'd like to know if that "progress is made" notion is possibly buggy. >> Specifically, does it mean "progress is made by this task"? Is it >> possible that resource contention creates a situation where most tasks >> in most cases can reclaim and allocate, but one task randomly fails to >> make progress? > > This can happen, alhtough it is quite unlikely. We are trying to > throttle allocations but you can hardly fight a consistent badluck ;) > > In order to see what is going on in your particular case we need an oom > report though. > -- > Michal Hocko > SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org