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=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 E6504C3A5A3 for ; Tue, 27 Aug 2019 10:43:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B35E9204EC for ; Tue, 27 Aug 2019 10:43:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1566902597; bh=DgzBwafkcWP7vXvi0ntkF77ZVB19ePV2F8i3vcXt+uo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=IGJ0zNbXAoKBait0OwzLPqd8b1YVOirkPhPTXWcXkwEfftrQk6eZ11E/7kH+DyOyj 0pOx+j43+Fqg3IWT/06DwmSf9l/2p+rTeAvhcOINFOKdCJUgFGujy1li5AipslrYQ4 B3l4oQiuWi10OVybVLEOUPYGBV0zudx06bjBLIQg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727815AbfH0KnQ (ORCPT ); Tue, 27 Aug 2019 06:43:16 -0400 Received: from mx2.suse.de ([195.135.220.15]:53470 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725793AbfH0KnQ (ORCPT ); Tue, 27 Aug 2019 06:43:16 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 1C68BAFD4; Tue, 27 Aug 2019 10:43:15 +0000 (UTC) Date: Tue, 27 Aug 2019 12:43:13 +0200 From: Michal Hocko To: Yang Shi 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 Subject: Re: WARNINGs in set_task_reclaim_state with memory cgroup and full memory usage Message-ID: <20190827104313.GW7538@dhcp22.suse.cz> References: <20190826105521.GF7538@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190826105521.GF7538@dhcp22.suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. > > 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 -- Michal Hocko SUSE Labs