From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 96C0DC04AA5 for ; Mon, 15 Oct 2018 12:47:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1BB502064A for ; Mon, 15 Oct 2018 12:47:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1BB502064A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=i-love.sakura.ne.jp Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726628AbeJOUc2 (ORCPT ); Mon, 15 Oct 2018 16:32:28 -0400 Received: from www262.sakura.ne.jp ([202.181.97.72]:33551 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726319AbeJOUc2 (ORCPT ); Mon, 15 Oct 2018 16:32:28 -0400 Received: from fsav103.sakura.ne.jp (fsav103.sakura.ne.jp [27.133.134.230]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id w9FClEhF091008; Mon, 15 Oct 2018 21:47:14 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav103.sakura.ne.jp (F-Secure/fsigk_smtp/530/fsav103.sakura.ne.jp); Mon, 15 Oct 2018 21:47:14 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/530/fsav103.sakura.ne.jp) Received: from [192.168.1.8] (softbank060157066051.bbtec.net [60.157.66.51]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id w9FClAgN090934 (version=TLSv1.2 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Mon, 15 Oct 2018 21:47:14 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Subject: Re: [RFC PATCH] memcg, oom: throttle dump_header for memcg ooms without eligible tasks To: Michal Hocko Cc: Johannes Weiner , linux-mm@kvack.org, syzkaller-bugs@googlegroups.com, guro@fb.com, kirill.shutemov@linux.intel.com, linux-kernel@vger.kernel.org, rientjes@google.com, yang.s@alibaba-inc.com, Andrew Morton , Sergey Senozhatsky , Petr Mladek , Sergey Senozhatsky , Steven Rostedt References: <20181012112008.GA27955@cmpxchg.org> <20181012120858.GX5873@dhcp22.suse.cz> <9174f087-3f6f-f0ed-6009-509d4436a47a@i-love.sakura.ne.jp> <20181012124137.GA29330@cmpxchg.org> <0417c888-d74e-b6ae-a8f0-234cbde03d38@i-love.sakura.ne.jp> <20181013112238.GA762@cmpxchg.org> <20181015081934.GD18839@dhcp22.suse.cz> <20181015112427.GI18839@dhcp22.suse.cz> From: Tetsuo Handa Message-ID: <6c0a57b3-bfd4-d832-b0bd-5dd3bcae460e@i-love.sakura.ne.jp> Date: Mon, 15 Oct 2018 21:47:08 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20181015112427.GI18839@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2018/10/15 20:24, Michal Hocko wrote: > On Mon 15-10-18 19:57:35, Tetsuo Handa wrote: >> On 2018/10/15 17:19, Michal Hocko wrote: >>> As so many dozens of times before, I will point you to an incremental >>> nature of changes we really prefer in the mm land. We are also after a >>> simplicity which your proposal lacks in many aspects. You seem to ignore >>> that general approach and I have hard time to consider your NAK as a >>> relevant feedback. Going to an extreme and basing a complex solution on >>> it is not going to fly. No killable process should be a rare event which >>> requires a seriously misconfigured memcg to happen so wildly. If you can >>> trigger it with a normal user privileges then it would be a clear bug to >>> address rather than work around with printk throttling. >>> >> >> I can trigger 200+ times / 900+ lines / 69KB+ of needless OOM messages >> with a normal user privileges. This is a lot of needless noise/delay. > > I am pretty sure you have understood the part of my message you have > chosen to not quote where I have said that the specific rate limitting > decisions can be changed based on reasonable configurations. There is > absolutely zero reason to NAK a natural decision to unify the throttling > and cook a per-memcg way for a very specific path instead. > >> No killable process is not a rare event, even without root privileges. >> >> [root@ccsecurity kumaneko]# time ./a.out >> Killed >> >> real 0m2.396s >> user 0m0.000s >> sys 0m2.970s >> [root@ccsecurity ~]# dmesg | grep 'no killable' | wc -l >> 202 >> [root@ccsecurity ~]# dmesg | wc >> 942 7335 70716 > > OK, so this is 70kB worth of data pushed throug the console. Is this > really killing any machine? > Nobody can prove that it never kills some machine. This is just one example result of one example stress tried in my environment. Since I am secure programming man from security subsystem, I really hate your "Can you trigger it?" resistance. Since this is OOM path where nobody tests, starting from being prepared for the worst case keeps things simple.