From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f199.google.com (mail-pf0-f199.google.com [209.85.192.199]) by kanga.kvack.org (Postfix) with ESMTP id 637B46B0005 for ; Thu, 26 Apr 2018 15:05:18 -0400 (EDT) Received: by mail-pf0-f199.google.com with SMTP id z22so15069623pfi.7 for ; Thu, 26 Apr 2018 12:05:18 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id f14si10845385pgu.612.2018.04.26.12.05.17 for (version=TLS1 cipher=AES128-SHA bits=128/128); Thu, 26 Apr 2018 12:05:17 -0700 (PDT) Date: Thu, 26 Apr 2018 21:05:14 +0200 From: Michal Hocko Subject: Re: OOM killer invoked while still one forth of mem is available Message-ID: <20180426190514.GU17484@dhcp22.suse.cz> References: <296ea83c-2c00-f1d2-3f62-d8ab8b8fb73c@c-s.fr> <20180426131154.GQ17484@dhcp22.suse.cz> <2706829f-6207-89f7-46e6-d32244305ccb@c-s.fr> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <2706829f-6207-89f7-46e6-d32244305ccb@c-s.fr> Sender: owner-linux-mm@kvack.org List-ID: To: Christophe LEROY Cc: David Rientjes , linux-mm@kvack.org, "linuxppc-dev@lists.ozlabs.org" On Thu 26-04-18 15:28:46, Christophe LEROY wrote: > > > Le 26/04/2018 a 15:11, Michal Hocko a ecrit : > > On Thu 26-04-18 08:10:30, Christophe LEROY wrote: > > > > > > > > > Le 25/04/2018 a 21:57, David Rientjes a ecrit : > > > > On Tue, 24 Apr 2018, christophe leroy wrote: > > > > > > > > > Hi > > > > > > > > > > Allthough there is still about one forth of memory available (7976kB > > > > > among 32MB), oom-killer is invoked and makes a victim. > > > > > > > > > > What could be the reason and how could it be solved ? > > > > > > > > > > [ 54.400754] S99watchdogd-ap invoked oom-killer: > > > > > gfp_mask=0x27000c0(GFP_KERNEL_ACCOUNT|__GFP_NOTRACK), nodemask=0, > > > > > order=1, oom_score_adj=0 > > > > > [ 54.400815] CPU: 0 PID: 777 Comm: S99watchdogd-ap Not tainted > > > > > 4.9.85-local-knld-998 #5 > > > > > [ 54.400830] Call Trace: > > > > > [ 54.400910] [c1ca5d10] [c0327d28] dump_header.isra.4+0x54/0x17c > > > > > (unreliable) > > > > > [ 54.400998] [c1ca5d50] [c0079d88] oom_kill_process+0xc4/0x414 > > > > > [ 54.401067] [c1ca5d90] [c007a5c8] out_of_memory+0x35c/0x37c > > > > > [ 54.401220] [c1ca5dc0] [c007d68c] __alloc_pages_nodemask+0x8ec/0x9a8 > > > > > [ 54.401318] [c1ca5e70] [c00169d4] copy_process.isra.9.part.10+0xdc/0x10d0 > > > > > [ 54.401398] [c1ca5f00] [c0017b30] _do_fork+0xcc/0x2a8 > > > > > [ 54.401473] [c1ca5f40] [c000a660] ret_from_syscall+0x0/0x38 > > > > > > > > Looks like this is because the allocation is order-1, likely the > > > > allocation of a struct task_struct for a new process on fork. > > > > > > I'm not sure I understand what you mean. The allocation is order 1, yes, > > > does it explains why OOM killer is invoked ? > > > > Well, not really > > [ 54.437414] DMA: 460*4kB (UH) 201*8kB (UH) 121*16kB (UH) 43*32kB (UH) 10*64kB (U) 4*128kB (UH) 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB 0*8192kB = 7912kB` > > > > You should have enough order-1+ pages to proceed. > > > > So, order is 1 so order - 1 is 0, Not sure what you mean by order - 1, maybe I've confused you. order-1 means that the order is 1. So free is not all that important. What you should look at though is how many order 1+ free blocks are available. > what's wrong then ? Do the (UH) and (U) > means anything special ? Yes, show_migration_types. But I do not see why unmovable pageblocks should block the allocation. This is a GFP_KERNEL allocation request essentially - thus unmovable itself. This smells like a bug. We are way above reserves which could block the allocation. > Otherwise, just above it says 'free:1994', so with > 1994 pages free I should have enough to proceed, shouldn't I ? Not for high order pages as per above... -- Michal Hocko SUSE Labs