From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f180.google.com (mail-io0-f180.google.com [209.85.223.180]) by kanga.kvack.org (Postfix) with ESMTP id 247676B0254 for ; Wed, 20 Jan 2016 10:55:07 -0500 (EST) Received: by mail-io0-f180.google.com with SMTP id q21so23985602iod.0 for ; Wed, 20 Jan 2016 07:55:07 -0800 (PST) Received: from www262.sakura.ne.jp (www262.sakura.ne.jp. [2001:e42:101:1:202:181:97:72]) by mx.google.com with ESMTPS id b1si43979625igt.31.2016.01.20.07.55.05 for (version=TLS1 cipher=AES128-SHA bits=128/128); Wed, 20 Jan 2016 07:55:06 -0800 (PST) Subject: Re: [BUG] oom hangs the system, NMI backtrace shows most CPUs in shrink_slab From: Tetsuo Handa References: <569E1010.2070806@I-love.SAKURA.ne.jp> <569E5287.4080503@redhat.com> <201601201923.DCC48978.FSHLOQtOVJFFOM@I-love.SAKURA.ne.jp> <201601202217.BEF43262.QOLFHOOJFVFtMS@I-love.SAKURA.ne.jp> <20160120151044.GA5157@mtj.duckdns.org> In-Reply-To: <20160120151044.GA5157@mtj.duckdns.org> Message-Id: <201601210054.CEG04187.VFMQOFHOOLJFtS@I-love.SAKURA.ne.jp> Date: Thu, 21 Jan 2016 00:54:56 +0900 Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org List-ID: To: tj@kernel.org Cc: jiangshanlai@gmail.com, jstancek@redhat.com, linux-mm@kvack.org, ltp@lists.linux.it Tejun Heo wrote: > On Wed, Jan 20, 2016 at 10:17:23PM +0900, Tetsuo Handa wrote: > > What happens if memory allocation requests from items using this workqueue > > got stuck due to OOM livelock? Are pending items in this workqueue cannot > > be processed because this workqueue was created without WQ_MEM_RECLAIM? > > If something gets stuck due to OOM livelock, anything which tries to > allocate memory can hang. That's why it's called a livelock. > WQ_MEM_RECLAIM or not wouldn't make any difference. > > > I don't know whether accessing swap memory depends on this workqueue. > > But if disk driver depends on this workqueue for accessing swap partition > > on the disk, some event is looping inside memory allocator will result in > > unable to process disk I/O request for accessing swap partition on the disk? > > What you're saying is too vauge for me to decipher exactly what you > have on mind. Can you please elaborate? > In this thread ( http://lkml.kernel.org/r/569D06F8.4040209@redhat.com ) Jan hit an OOM stall where free memory does not increase even after OOM victim and dying tasks terminated. I'm wondering why such thing can happen. Since "Swap cache stats:" stopped increasing immediately after the OOM stall began, I'm suspecting possibility that disk I/O event which is needed for accessing swap memory is deferred due to cdrom I/O event stalling at memory allocation when that disk I/O event is needed for increasing free memory. [ 6915.253288] MemAlloc: kworker/1:1(20708) seq=48 gfp=0x2400000 order=0 delay=20248 [ 6915.301353] MemAlloc: oom01(22011) seq=5135 gfp=0x24280ca order=0 delay=20641 [ 6915.317280] MemAlloc: oom01(22013) seq=5101 gfp=0x24280ca order=0 delay=20641 Maybe retesting with show_workqueue_state() added answers my question. -- 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