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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, UNPARSEABLE_RELAY,USER_AGENT_SANE_1 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 0334AC3A5A3 for ; Tue, 27 Aug 2019 17:12:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D6C07214DA for ; Tue, 27 Aug 2019 17:12:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729616AbfH0RMi (ORCPT ); Tue, 27 Aug 2019 13:12:38 -0400 Received: from out30-132.freemail.mail.aliyun.com ([115.124.30.132]:33724 "EHLO out30-132.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727057AbfH0RMi (ORCPT ); Tue, 27 Aug 2019 13:12:38 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R101e4;CH=green;DM=||false|;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04407;MF=yang.shi@linux.alibaba.com;NM=1;PH=DS;RN=10;SR=0;TI=SMTPD_---0Tacy7tn_1566925936; Received: from US-143344MP.local(mailfrom:yang.shi@linux.alibaba.com fp:SMTPD_---0Tacy7tn_1566925936) by smtp.aliyun-inc.com(127.0.0.1); Wed, 28 Aug 2019 01:12:20 +0800 Subject: Re: WARNINGs in set_task_reclaim_state with memory cgroup and full memory usage To: Michal Hocko Cc: Adric Blake , akpm@linux-foundation.org, ktkhai@virtuozzo.com, hannes@cmpxchg.org, daniel.m.jordan@oracle.com, laoar.shao@gmail.com, mgorman@techsingularity.net, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20190826105521.GF7538@dhcp22.suse.cz> <20190827104313.GW7538@dhcp22.suse.cz> From: Yang Shi Message-ID: <6bbdd982-8c33-0a07-b8ea-5bd1be594b6e@linux.alibaba.com> Date: Tue, 27 Aug 2019 10:12:07 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <20190827104313.GW7538@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/27/19 3:43 AM, Michal Hocko wrote: > If there are no objection to the patch I will post it as a standalong > one. > > On Mon 26-08-19 12:55:21, Michal Hocko wrote: >> From 59d128214a62bf2d83c2a2a9cde887b4817275e7 Mon Sep 17 00:00:00 2001 >> From: Michal Hocko >> Date: Mon, 26 Aug 2019 12:43:15 +0200 >> Subject: [PATCH] mm, memcg: do not set reclaim_state on soft limit reclaim >> >> Adric Blake has noticed the following warning: >> [38491.963105] WARNING: CPU: 7 PID: 175 at mm/vmscan.c:245 set_task_reclaim_state+0x1e/0x40 >> [...] >> [38491.963239] Call Trace: >> [38491.963246] mem_cgroup_shrink_node+0x9b/0x1d0 >> [38491.963250] mem_cgroup_soft_limit_reclaim+0x10c/0x3a0 >> [38491.963254] balance_pgdat+0x276/0x540 >> [38491.963258] kswapd+0x200/0x3f0 >> [38491.963261] ? wait_woken+0x80/0x80 >> [38491.963265] kthread+0xfd/0x130 >> [38491.963267] ? balance_pgdat+0x540/0x540 >> [38491.963269] ? kthread_park+0x80/0x80 >> [38491.963273] ret_from_fork+0x35/0x40 >> [38491.963276] ---[ end trace 727343df67b2398a ]--- >> >> which tells us that soft limit reclaim is about to overwrite the >> reclaim_state configured up in the call chain (kswapd in this case but >> the direct reclaim is equally possible). This means that reclaim stats >> would get misleading once the soft reclaim returns and another reclaim >> is done. >> >> Fix the warning by dropping set_task_reclaim_state from the soft reclaim >> which is always called with reclaim_state set up. This is exactly what I thought. Looks good to me. Acked-by: Yang Shi >> >> Reported-by: Adric Blake >> Signed-off-by: Michal Hocko >> --- >> mm/vmscan.c | 5 +++-- >> 1 file changed, 3 insertions(+), 2 deletions(-) >> >> diff --git a/mm/vmscan.c b/mm/vmscan.c >> index c77d1e3761a7..a6c5d0b28321 100644 >> --- a/mm/vmscan.c >> +++ b/mm/vmscan.c >> @@ -3220,6 +3220,7 @@ unsigned long try_to_free_pages(struct zonelist *zonelist, int order, >> >> #ifdef CONFIG_MEMCG >> >> +/* Only used by soft limit reclaim. Do not reuse for anything else. */ >> unsigned long mem_cgroup_shrink_node(struct mem_cgroup *memcg, >> gfp_t gfp_mask, bool noswap, >> pg_data_t *pgdat, >> @@ -3235,7 +3236,8 @@ unsigned long mem_cgroup_shrink_node(struct mem_cgroup *memcg, >> }; >> unsigned long lru_pages; >> >> - set_task_reclaim_state(current, &sc.reclaim_state); >> + WARN_ON_ONCE(!current->reclaim_state); >> + >> sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | >> (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); >> >> @@ -3253,7 +3255,6 @@ unsigned long mem_cgroup_shrink_node(struct mem_cgroup *memcg, >> >> trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed); >> >> - set_task_reclaim_state(current, NULL); >> *nr_scanned = sc.nr_scanned; >> >> return sc.nr_reclaimed; >> -- >> 2.20.1 >> >> -- >> Michal Hocko >> SUSE Labs