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=-9.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 41966C43461 for ; Wed, 16 Sep 2020 06:08:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DF7AA2087D for ; Wed, 16 Sep 2020 06:08:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726314AbgIPGIT (ORCPT ); Wed, 16 Sep 2020 02:08:19 -0400 Received: from mx2.suse.de ([195.135.220.15]:58698 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726183AbgIPGIQ (ORCPT ); Wed, 16 Sep 2020 02:08:16 -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 8CDB6AAC7; Wed, 16 Sep 2020 06:08:29 +0000 (UTC) Date: Wed, 16 Sep 2020 08:08:08 +0200 From: Michal Hocko To: zangchunxin@bytedance.com Cc: akpm@linux-foundation.org, chris@chrisdown.name, vbabka@suse.cz, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Muchun Song Subject: Re: [PATCH v5] mm/vmscan: add a fatal signals check in drop_slab_node Message-ID: <20200916060808.GA18998@dhcp22.suse.cz> References: <20200916025359.70203-1-zangchunxin@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200916025359.70203-1-zangchunxin@bytedance.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 16-09-20 10:53:59, zangchunxin@bytedance.com wrote: > From: Chunxin Zang > > On our server, there are about 10k memcg in one machine. They use memory > very frequently. We have observed that drop_caches can take a > considerable amount of time, and can't stop it. > > There are two reasons: > 1. There is somebody constantly generating more objects to reclaim > on drop_caches, result the 'freed' always bigger than 10. > 2. The process has no chance to process signals. > > We can get the following info through 'ps': > > root:~# ps -aux | grep drop > root 357956 ... R Aug25 21119854:55 echo 3 > /proc/sys/vm/drop_caches > root 1771385 ... R Aug16 21146421:17 echo 3 > /proc/sys/vm/drop_caches > > Add a bail out on the fatal signals in the main loop so that the > operation can be terminated by userspace. > > Signed-off-by: Chunxin Zang > Signed-off-by: Muchun Song Acked-by: Michal Hocko > --- > changelogs in v5: > 1) v4 patch used wrong branch, very apologies about that. > > changelogs in v4: > changelogs in v3: > 1) Fix some descriptive problems pointed out by Michal Hocko. > v2 named: mm/vmscan: fix infinite loop in drop_slab_node > > changelogs in v2: > 1) via check fatal signal break loop. > > mm/vmscan.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index b6d84326bdf2..c3ed8b45d264 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -704,6 +704,9 @@ void drop_slab_node(int nid) > do { > struct mem_cgroup *memcg = NULL; > > + if (fatal_signal_pending(current)) > + return; > + > freed = 0; > memcg = mem_cgroup_iter(NULL, NULL, NULL); > do { > -- > 2.11.0 > -- Michal Hocko SUSE Labs