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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 E5D2DC433DB for ; Wed, 10 Feb 2021 09:50:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9CE2D64E40 for ; Wed, 10 Feb 2021 09:50:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229816AbhBJJuC (ORCPT ); Wed, 10 Feb 2021 04:50:02 -0500 Received: from mx2.suse.de ([195.135.220.15]:46478 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229610AbhBJJsh (ORCPT ); Wed, 10 Feb 2021 04:48:37 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1612950468; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=fdOKlGdBQ+hhHPE98TkFop+2UQxW0u+WMNNhnyafX9Q=; b=TH4zS6eBWoevbm4jAsK0+oZMMY2MFI6CHMoLEJY2Jj0ho1cPXvNBVdNcmpQz+y80cOz2pb lT5RtH88wV0Q+o3pZSJjNtoCvVw7QPP5KzSk4hyJZqBNGWhjiGGgqEoySHGkUceUMYIZal b3CKioh8b9ixkAWkmkaSPdNs/EKGI9A= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 3FC32AD57; Wed, 10 Feb 2021 09:47:48 +0000 (UTC) Date: Wed, 10 Feb 2021 10:47:44 +0100 From: Michal Hocko To: Tim Chen Cc: Andrew Morton , Johannes Weiner , Vladimir Davydov , Dave Hansen , Ying Huang , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/3] mm: Fix dropped memcg from mem cgroup soft limit tree Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 09-02-21 12:29:45, Tim Chen wrote: > During soft limit memory reclaim, we will temporarily remove the target > mem cgroup from the cgroup soft limit tree. We then perform memory > reclaim, update the memory usage excess count and re-insert the mem > cgroup back into the mem cgroup soft limit tree according to the new > memory usage excess count. > > However, when memory reclaim failed for a maximum number of attempts > and we bail out of the reclaim loop, we forgot to put the target mem > cgroup chosen for next reclaim back to the soft limit tree. This prevented > pages in the mem cgroup from being reclaimed in the future even though > the mem cgroup exceeded its soft limit. Fix the logic and put the mem > cgroup back on the tree when page reclaim failed for the mem cgroup. > > Reviewed-by: Ying Huang > Signed-off-by: Tim Chen It seems this goes all the way to when it has been introduced by 4e41695356fb ("memory controller: soft limit reclaim on contention"). Please add a Fixes tag pointing to the above one. While this looks like a rare event to happen because there should be some reclaimable memory usually. Acked-by: Michal Hocko Thanks! > --- > mm/memcontrol.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index ed5cc78a8dbf..a51bf90732cb 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -3505,8 +3505,12 @@ unsigned long mem_cgroup_soft_limit_reclaim(pg_data_t *pgdat, int order, > loop > MEM_CGROUP_MAX_SOFT_LIMIT_RECLAIM_LOOPS)) > break; > } while (!nr_reclaimed); > - if (next_mz) > + if (next_mz) { > + spin_lock_irq(&mctz->lock); > + __mem_cgroup_insert_exceeded(next_mz, mctz, excess); > + spin_unlock_irq(&mctz->lock); > css_put(&next_mz->memcg->css); > + } > return nr_reclaimed; > } > > -- > 2.20.1 -- Michal Hocko SUSE Labs