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=-9.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS 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 2E101C433DF for ; Wed, 26 Aug 2020 15:05:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1250E207BC for ; Wed, 26 Aug 2020 15:05:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727923AbgHZPF2 (ORCPT ); Wed, 26 Aug 2020 11:05:28 -0400 Received: from mx2.suse.de ([195.135.220.15]:45004 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727814AbgHZPFU (ORCPT ); Wed, 26 Aug 2020 11:05:20 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 511F9AC46; Wed, 26 Aug 2020 15:05:50 +0000 (UTC) Date: Wed, 26 Aug 2020 17:05:17 +0200 From: Michal Hocko To: Xunlei Pang Cc: Johannes Weiner , Andrew Morton , Vladimir Davydov , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v2] mm: memcg: Fix memcg reclaim soft lockup Message-ID: <20200826150517.GS22869@dhcp22.suse.cz> References: <1598449622-108748-1-git-send-email-xlpang@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1598449622-108748-1-git-send-email-xlpang@linux.alibaba.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 26-08-20 21:47:02, Xunlei Pang wrote: > 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() at the upper shrink_node_memcgs() to solve this > issue, and any other possible issue like meomry.min protection. I would just add " This will mean that we will get a scheduling point for each memcg in the reclaimed hierarchy without any dependency on the reclaimable memory in that memcg thus making it more predictable. " > Suggested-by: Michal Hocko > Signed-off-by: Xunlei Pang Acked-by: Michal Hocko Thanks! > --- > mm/vmscan.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 99e1796..bbdc38b 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -2617,6 +2617,8 @@ static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc) > > mem_cgroup_calculate_protection(target_memcg, memcg); > > + cond_resched(); > + > if (mem_cgroup_below_min(memcg)) { > /* > * Hard protection. > -- > 1.8.3.1 -- Michal Hocko SUSE Labs