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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 11CDDC433EF for ; Mon, 1 Nov 2021 08:06:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EEC7C610CB for ; Mon, 1 Nov 2021 08:05:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231302AbhKAIIb (ORCPT ); Mon, 1 Nov 2021 04:08:31 -0400 Received: from szxga01-in.huawei.com ([45.249.212.187]:30888 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231608AbhKAII3 (ORCPT ); Mon, 1 Nov 2021 04:08:29 -0400 Received: from dggemv703-chm.china.huawei.com (unknown [172.30.72.55]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4HjQTL1yDDzcb0S; Mon, 1 Nov 2021 16:01:10 +0800 (CST) Received: from dggpeml500005.china.huawei.com (7.185.36.59) by dggemv703-chm.china.huawei.com (10.3.19.46) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.15; Mon, 1 Nov 2021 16:05:51 +0800 Received: from [10.174.178.155] (10.174.178.155) by dggpeml500005.china.huawei.com (7.185.36.59) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.2308.15; Mon, 1 Nov 2021 16:05:50 +0800 From: Yongqiang Liu To: CC: , , , , "Wangkefeng (OS Kernel Lab)" Subject: [QUESTION] oom killed the key system process triggered by a bad process alloc memory with MAP_LOCKED Message-ID: Date: Mon, 1 Nov 2021 16:05:50 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0 MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.178.155] X-ClientProxiedBy: dggeme702-chm.china.huawei.com (10.1.199.98) To dggpeml500005.china.huawei.com (7.185.36.59) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, I was just wondering the process of  the patch "oom reaper: handle mlocked pages". links: https://lore.kernel.org/linux-mm/1454505240-23446-3-git-send-email-mhocko@kernel.org/ https://lore.kernel.org/linux-mm/20160223132157.GD14178@dhcp22.suse.cz/ In linux master, we found that when we start a process and alloc large memory with MAP_LOCKED, the oom will triggered and kill some system process such as sshd ,rsyslog etc. ... [   45.110665] Out of memory: Killed process 2551 (oom) total-vm:1035324kB, anon-rss:1028196kB, file-rss:704kB, shmem-rss:0kB, UID:0 pgtables:2056kB oom_score_adj:1000 [   45.115303] Out of memory: Killed process 2554 (oom) total-vm:1025084kB, anon-rss:1015596kB, file-rss:388kB, shmem-rss:0kB, UID:0 pgtables:2032kB oom_score_adj:1000 [   45.115685] Out of memory: Killed process 2553 (oom) total-vm:953404kB, anon-rss:947748kB, file-rss:388kB, shmem-rss:0kB, UID:0 pgtables:1896kB oom_score_adj:1000 [   45.116031] Out of memory: Killed process 2552 (oom) total-vm:789564kB, anon-rss:783272kB, file-rss:388kB, shmem-rss:0kB, UID:0 pgtables:1576kB oom_score_adj:1000 [   45.117199] Out of memory: Killed process 2523 (sshd) total-vm:77052kB, anon-rss:804kB, file-rss:4672kB, shmem-rss:4kB, UID:0 pgtables:196kB oom_score_adj:0 [   45.120936] Out of memory: Killed process 2526 (bash) total-vm:17792kB, anon-rss:1180kB, file-rss:2868kB, shmem-rss:0kB, UID:0 pgtables:76kB oom_score_adj:0 ... the process demo is: ... #define ALLOC_SIZE (10 * 1024 * 1024) while (1) {     addr = mmap(NULL, ALLOC_SIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_LOCKED, -1, 0);     if (addr != MAP_FAILED)         memset(addr, 1, ALLOC_SIZE); } ... And we found that when the oom_reaper is done but the memory is still high: [   45.115685] Out of memory: Killed process 2553 (oom) total-vm:953404kB, anon-rss:947748kB, file-rss:388kB, shmem-rss:0kB, UID:0 pgtables:1896kB oom_score_adj:1000 [   45.115739] oom_reaper: reaped process 2553 (oom), now anon-rss:947708kB, file-rss:0kB, shmem-rss:0kB This is because the bad proccess which recieved SIGKILL is unlocking the mem to exit which needs more time. And the next oom is triggered to kill the other system process. Kind regards, Yongqiang Liu