From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752279AbeDJHtY (ORCPT ); Tue, 10 Apr 2018 03:49:24 -0400 Received: from mx2.suse.de ([195.135.220.15]:40258 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752052AbeDJHtX (ORCPT ); Tue, 10 Apr 2018 03:49:23 -0400 Date: Tue, 10 Apr 2018 09:49:21 +0200 From: Michal Hocko To: Zhaoyang Huang Cc: Steven Rostedt , Ingo Molnar , LKML Subject: Re: [PATCH v1] ringbuffer: Don't choose the process with adj equal OOM_SCORE_ADJ_MIN Message-ID: <20180410074921.GU21835@dhcp22.suse.cz> References: <20180408084717.62ee4f9e@gandalf.local.home> <20180409094944.6399b211@gandalf.local.home> <20180409231230.1ab99e85@vmware.local.home> <20180410061447.GQ21835@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 10-04-18 14:39:35, Zhaoyang Huang wrote: > On Tue, Apr 10, 2018 at 2:14 PM, Michal Hocko wrote: > > On Tue 10-04-18 11:41:44, Zhaoyang Huang wrote: > >> On Tue, Apr 10, 2018 at 11:12 AM, Steven Rostedt wrote: > >> > On Tue, 10 Apr 2018 10:32:36 +0800 > >> > Zhaoyang Huang wrote: > >> > > >> >> For bellowing scenario, process A have no intension to exhaust the > >> >> memory, but will be likely to be selected by OOM for we set > >> >> OOM_CORE_ADJ_MIN for it. > >> >> process A(-1000) process B > >> >> > >> >> i = si_mem_available(); > >> >> if (i < nr_pages) > >> >> return -ENOMEM; > >> >> schedule > >> >> ---------------> > >> >> allocate huge memory > >> >> <------------- > >> >> if (user_thread) > >> >> set_current_oom_origin(); > >> >> > >> >> for (i = 0; i < nr_pages; i++) { > >> >> bpage = kzalloc_node > >> > > >> > Is this really an issue though? > >> > > >> > Seriously, do you think you will ever hit this? > >> > > >> > How often do you increase the size of the ftrace ring buffer? For this > >> > to be an issue, the system has to trigger an OOM at the exact moment > >> > you decide to increase the size of the ring buffer. That would be an > >> > impressive attack, with little to gain. > >> > > >> > Ask the memory management people. If they think this could be a > >> > problem, then I'll be happy to take your patch. > >> > > >> > -- Steve > >> add Michael for review. > >> Hi Michael, > >> I would like suggest Steve NOT to set OOM_CORE_ADJ_MIN for the process > >> with adj = -1000 when setting the user space process as potential > >> victim of OOM. > > > > OOM_SCORE_ADJ_MIN means "hide the process from the OOM killer completely". > > So what exactly do you want to achieve here? Because from the above it > > sounds like opposite things. /me confused... > > > Steve's patch intend to have the process be OOM's victim when it > over-allocating pages for ring buffer. I amend a patch over to protect > process with OOM_SCORE_ADJ_MIN from doing so. Because it will make > such process to be selected by current OOM's way of > selecting.(consider OOM_FLAG_ORIGIN first before the adj) I just wouldn't really care unless there is an existing and reasonable usecase for an application which updates the ring buffer size _and_ it is OOM disabled at the same time. -- Michal Hocko SUSE Labs