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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 16A3DC433B4 for ; Sat, 24 Apr 2021 16:19:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D8E0D6120D for ; Sat, 24 Apr 2021 16:19:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232051AbhDXQUg convert rfc822-to-8bit (ORCPT ); Sat, 24 Apr 2021 12:20:36 -0400 Received: from jptosegrel01.sonyericsson.com ([124.215.201.71]:13009 "EHLO JPTOSEGREL01.sonyericsson.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230010AbhDXQUf (ORCPT ); Sat, 24 Apr 2021 12:20:35 -0400 Subject: Re: [RFC PATCH] watchdog: Adding softwatchdog To: Tetsuo Handa , Guenter Roeck , Wim Van Sebroeck , Andrew Morton , , , , Shakeel Butt References: <20210424102555.28203-1-peter.enderborg@sony.com> <20210424102555.28203-2-peter.enderborg@sony.com> <844e3ecb-62c3-856a-7273-e22eee35e80f@i-love.sakura.ne.jp> From: peter enderborg Message-ID: Date: Sat, 24 Apr 2021 18:19:52 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <844e3ecb-62c3-856a-7273-e22eee35e80f@i-love.sakura.ne.jp> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8BIT Content-Language: en-GB X-SEG-SpamProfiler-Analysis: v=2.3 cv=DLnxHBFb c=1 sm=1 tr=0 a=fZcToFWbXLKijqHhjJ02CA==:117 a=IkcTkHD0fZMA:10 a=3YhXtTcJ-WEA:10 a=ZvUQ5lN1LNaykfZji70A:9 a=QEXdDO2ut3YA:10 X-SEG-SpamProfiler-Score: 0 Precedence: bulk List-ID: X-Mailing-List: linux-watchdog@vger.kernel.org On 4/24/21 5:23 PM, Tetsuo Handa wrote: > On 2021/04/24 23:41, Guenter Roeck wrote: >> On 4/24/21 3:25 AM, Peter Enderborg wrote: >>> This is not a rebooting watchdog. It's function is to take other >>> actions than a hard reboot. On many complex system there is some >>> kind of manager that monitor and take action on slow systems. >>> Android has it's lowmemorykiller (lmkd), desktops has earlyoom. >>> This watchdog can be used to help monitor to preform some basic >>> action to keep the monitor running. >>> >>> It can also be used standalone. This add a policy that is >>> killing the process with highest oom_score_adj and using >>> oom functions to it quickly. I think it is a good usecase >>> for the patch. Memory siuations can be problematic for >>> software that monitor system, but other prolicys can >>> should also be possible. Like picking tasks from a memcg, or >>> specific UID's or what ever is low priority. >>> --- >> NACK. Besides this not following the new watchdog API, the task >> of a watchdog is to reset the system on failure. Its task is most >> definitely not to re-implement the oom killer in any way, shape, >> or form. >> > I don't think this proposal is a watchdog. I think this proposal is > a timer based process killer, based on an assumption that any slowdown > which prevents the monitor process from pinging for more than 0.5 seconds > (if HZ == 1000) is caused by memory pressure. You missing the point. The oom killer is a example of a work that it can do. it is one policy. The idea is that you should have a policy that fits your needs. oom_score_adj is suitable for a android world. But it might be based on uid's if your priority is some users over other.  Or a memcg. Or as Christophe Leroy want the current. The policy is only a example that fits a one area. You need to describe your prioritization, in android it is oom_score_adj. For example I would very much have a policy that sends sigterm instead of sigkill. But the integration with oom is there because it is needed. Maybe a bad choice for political reasons but I don't it a good idea to hide the intention. Please don't focus on the oom part.