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=-12.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,USER_AGENT_GIT autolearn=ham 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 0608CC433DF for ; Wed, 26 Aug 2020 07:27:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D20992071E for ; Wed, 26 Aug 2020 07:27:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726862AbgHZH1r (ORCPT ); Wed, 26 Aug 2020 03:27:47 -0400 Received: from out30-45.freemail.mail.aliyun.com ([115.124.30.45]:32921 "EHLO out30-45.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726716AbgHZH1o (ORCPT ); Wed, 26 Aug 2020 03:27:44 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R921e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e01355;MF=xlpang@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0U6u0vBE_1598426822; Received: from localhost(mailfrom:xlpang@linux.alibaba.com fp:SMTPD_---0U6u0vBE_1598426822) by smtp.aliyun-inc.com(127.0.0.1); Wed, 26 Aug 2020 15:27:40 +0800 From: Xunlei Pang To: Johannes Weiner , Michal Hocko , Andrew Morton , Vladimir Davydov Cc: Xunlei Pang , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH] mm: memcg: Fix memcg reclaim soft lockup Date: Wed, 26 Aug 2020 15:27:02 +0800 Message-Id: <1598426822-93737-1-git-send-email-xlpang@linux.alibaba.com> X-Mailer: git-send-email 1.8.3.1 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org We've met softlockup with "CONFIG_PREEMPT_NONE=y", when the target memcg doesn't have any reclaimable memory. It can be easily reproduced as below: watchdog: BUG: soft lockup - CPU#0 stuck for 111s![memcg_test:2204] CPU: 0 PID: 2204 Comm: memcg_test Not tainted 5.9.0-rc2+ #12 Call Trace: shrink_lruvec+0x49f/0x640 shrink_node+0x2a6/0x6f0 do_try_to_free_pages+0xe9/0x3e0 try_to_free_mem_cgroup_pages+0xef/0x1f0 try_charge+0x2c1/0x750 mem_cgroup_charge+0xd7/0x240 __add_to_page_cache_locked+0x2fd/0x370 add_to_page_cache_lru+0x4a/0xc0 pagecache_get_page+0x10b/0x2f0 filemap_fault+0x661/0xad0 ext4_filemap_fault+0x2c/0x40 __do_fault+0x4d/0xf9 handle_mm_fault+0x1080/0x1790 It only happens on our 1-vcpu instances, because there's no chance for oom reaper to run to reclaim the to-be-killed process. Add cond_resched() in such cases at the beginning of shrink_lruvec() to give up the cpu to others. Signed-off-by: Xunlei Pang --- mm/vmscan.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/mm/vmscan.c b/mm/vmscan.c index 99e1796..349a88e 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2449,6 +2449,12 @@ static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc) scan_adjusted = (!cgroup_reclaim(sc) && !current_is_kswapd() && sc->priority == DEF_PRIORITY); + /* memcg reclaim may run into no reclaimable lru pages */ + if (nr[LRU_ACTIVE_FILE] == 0 && + nr[LRU_INACTIVE_FILE] == 0 && + nr[LRU_INACTIVE_ANON] == 0) + cond_resched(); + blk_start_plug(&plug); while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] || nr[LRU_INACTIVE_FILE]) { -- 1.8.3.1