From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752594AbeDJGji (ORCPT ); Tue, 10 Apr 2018 02:39:38 -0400 Received: from mail-wm0-f66.google.com ([74.125.82.66]:53842 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751820AbeDJGjg (ORCPT ); Tue, 10 Apr 2018 02:39:36 -0400 X-Google-Smtp-Source: AIpwx4+SUpFQbyKTx82InlnJaEwnDxb5AJYW0x8DIsayF9+xYJtuFyztDNmgN1qLSKuld9gFEI4QMGfh3QsuTm80iFU= MIME-Version: 1.0 In-Reply-To: <20180410061447.GQ21835@dhcp22.suse.cz> References: <1523153783-20579-1-git-send-email-zhaoyang.huang@spreadtrum.com> <20180407234812.2bf2b24b@gandalf.local.home> <20180408084717.62ee4f9e@gandalf.local.home> <20180409094944.6399b211@gandalf.local.home> <20180409231230.1ab99e85@vmware.local.home> <20180410061447.GQ21835@dhcp22.suse.cz> From: Zhaoyang Huang Date: Tue, 10 Apr 2018 14:39:35 +0800 Message-ID: Subject: Re: [PATCH v1] ringbuffer: Don't choose the process with adj equal OOM_SCORE_ADJ_MIN To: Michal Hocko Cc: Steven Rostedt , Ingo Molnar , LKML Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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... > > -- > Michal Hocko > SUSE Labs 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)