From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752078AbeDJDlq (ORCPT ); Mon, 9 Apr 2018 23:41:46 -0400 Received: from mail-wm0-f67.google.com ([74.125.82.67]:52605 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751833AbeDJDlp (ORCPT ); Mon, 9 Apr 2018 23:41:45 -0400 X-Google-Smtp-Source: AIpwx48gDT8AaC75aKS9yQuO1igoLrApJWV/c14LFJ7BtlXc6Ht4ntAGH85CTDdOcelIf9XdUfo5qyFPSAGnRpVSVEw= MIME-Version: 1.0 In-Reply-To: <20180409231230.1ab99e85@vmware.local.home> 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> From: Zhaoyang Huang Date: Tue, 10 Apr 2018 11:41:44 +0800 Message-ID: Subject: Re: [PATCH v1] ringbuffer: Don't choose the process with adj equal OOM_SCORE_ADJ_MIN To: Steven Rostedt , Michal Hocko Cc: 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 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. Steve doubts about the possibility of the scenario. In my opinion, we should NOT break the original concept of the OOM, that is, OOM would not select -1000 process unless it config it itself. With regard to the possibility, in memory thirsty system such as android on mobile phones, there are different kinds of user behavior or test script to attack or ensure the stability of the system. So I suggest we'd better keep every corner case safe. Would you please give a comment on that? thanks