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 A6F646B0005 for ; Thu, 21 Jul 2016 10:53:13 -0400 (EDT) Received: by mail-wm0-f69.google.com with SMTP id o80so15069053wme.1 for ; Thu, 21 Jul 2016 07:53:13 -0700 (PDT) Received: from mail-wm0-f67.google.com (mail-wm0-f67.google.com. [74.125.82.67]) by mx.google.com with ESMTPS id i196si3931677wmg.24.2016.07.21.07.53.12 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 21 Jul 2016 07:53:12 -0700 (PDT) Received: by mail-wm0-f67.google.com with SMTP id i5so2716660wmg.2 for ; Thu, 21 Jul 2016 07:53:12 -0700 (PDT) Date: Thu, 21 Jul 2016 16:53:10 +0200 From: Michal Hocko Subject: Re: [RFC PATCH 1/2] mempool: do not consume memory reserves from the reclaim path Message-ID: <20160721145309.GR26379@dhcp22.suse.cz> References: <1468831164-26621-1-git-send-email-mhocko@kernel.org> <1468831285-27242-1-git-send-email-mhocko@kernel.org> <20160719135426.GA31229@cmpxchg.org> <20160720081541.GF11249@dhcp22.suse.cz> <20160721085202.GC26379@dhcp22.suse.cz> <20160721121300.GA21806@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160721121300.GA21806@cmpxchg.org> Sender: owner-linux-mm@kvack.org List-ID: To: Johannes Weiner Cc: David Rientjes , linux-mm@kvack.org, Mikulas Patocka , Ondrej Kozina , Tetsuo Handa , Mel Gorman , Neil Brown , Andrew Morton , LKML , dm-devel@redhat.com On Thu 21-07-16 08:13:00, Johannes Weiner wrote: > On Thu, Jul 21, 2016 at 10:52:03AM +0200, Michal Hocko wrote: > > Look, there are > > $ git grep mempool_alloc | wc -l > > 304 > > > > many users of this API and we do not want to flip the default behavior > > which is there for more than 10 years. So far you have been arguing > > about potential deadlocks and haven't shown any particular path which > > would have a direct or indirect dependency between mempool and normal > > allocator and it wouldn't be a bug. As the matter of fact the change > > we are discussing here causes a regression. If you want to change the > > semantic of mempool allocator then you are absolutely free to do so. In > > a separate patch which would be discussed with IO people and other > > users, though. But we _absolutely_ want to fix the regression first > > and have a simple fix for 4.6 and 4.7 backports. At this moment there > > are revert and patch 1 on the table. The later one should make your > > backtrace happy and should be only as a temporal fix until we find out > > what is actually misbehaving on your systems. If you are not interested > > to pursue that way I will simply go with the revert. > > +1 > > It's very unlikely that decade-old mempool semantics are suddenly a > fundamental livelock problem, when all the evidence we have is one > hang and vague speculation. Given that the patch causes regressions, > and that the bug is most likely elsewhere anyway, a full revert rather > than merely-less-invasive mempool changes makes the most sense to me. OK, fair enough. What do you think about the following then? Mikulas, I have dropped your Tested-by and Reviewed-by because the patch is different but unless you have hit the OOM killer then the testing results should be same. ---