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=unavailable 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 1EAE1C433E1 for ; Wed, 26 Aug 2020 15:06:36 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id DD07F2078A for ; Wed, 26 Aug 2020 15:06:35 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DD07F2078A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 75C3A6B0006; Wed, 26 Aug 2020 11:06:35 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 708DA6B0007; Wed, 26 Aug 2020 11:06:35 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6205E6B0026; Wed, 26 Aug 2020 11:06:35 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0172.hostedemail.com [216.40.44.172]) by kanga.kvack.org (Postfix) with ESMTP id 4B6CA6B0006 for ; Wed, 26 Aug 2020 11:06:35 -0400 (EDT) Received: from smtpin05.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 1171C8248047 for ; Wed, 26 Aug 2020 15:06:35 +0000 (UTC) X-FDA: 77193046350.05.whip73_380006627065 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin05.hostedemail.com (Postfix) with ESMTP id 8118A18019255 for ; Wed, 26 Aug 2020 15:06:28 +0000 (UTC) X-HE-Tag: whip73_380006627065 X-Filterd-Recvd-Size: 3020 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf07.hostedemail.com (Postfix) with ESMTP for ; Wed, 26 Aug 2020 15:05:20 +0000 (UTC) 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> X-Rspamd-Queue-Id: 8118A18019255 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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