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=-15.7 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 99232C432BE for ; Mon, 2 Aug 2021 06:28:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 814E361042 for ; Mon, 2 Aug 2021 06:28:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232254AbhHBG2c (ORCPT ); Mon, 2 Aug 2021 02:28:32 -0400 Received: from smtp-out2.suse.de ([195.135.220.29]:60272 "EHLO smtp-out2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230432AbhHBG23 (ORCPT ); Mon, 2 Aug 2021 02:28:29 -0400 Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out2.suse.de (Postfix) with ESMTP id E07CA1FF2C; Mon, 2 Aug 2021 06:28:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1627885694; 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=6O4ovfEUNzace1WQB0NeGLBJmSbRWBaTfA/jz5eGKhU=; b=iekKpJ/FslvYsDvvZ82fpdm2vUtlLGMkBtK78wzaekb+Qk7ht7qwOi8jim1KAZlT5MBqOw /D4TEqIau7O5ebh+Rxwe4sF7sa2tsnufabuAG+xPb3GZ28ayU+B4ptzFRqQfydNDQqp4BV e5bwJxE3QHXGF43kpWrhdtZDLtlByAo= Received: from suse.cz (unknown [10.100.201.86]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id BC5BBA3BBE; Mon, 2 Aug 2021 06:28:13 +0000 (UTC) Date: Mon, 2 Aug 2021 08:28:13 +0200 From: Michal Hocko To: Waiman Long Cc: Johannes Weiner , Vladimir Davydov , Andrew Morton , Tejun Heo , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Vlastimil Babka , Roman Gushchin , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, Shakeel Butt , Muchun Song , Alex Shi , Chris Down , Yafang Shao , Wei Yang , Masayoshi Mizuma , Xing Zhengjun , Matthew Wilcox Subject: Re: [PATCH] mm/memcg: Fix incorrect flushing of lruvec data in obj_stock Message-ID: References: <20210802022827.10192-1-longman@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210802022827.10192-1-longman@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun 01-08-21 22:28:27, Waiman Long wrote: > When mod_objcg_state() is called with a pgdat that is different from > that in the obj_stock, the old lruvec data cached in obj_stock are > flushed out. Unfortunately, they were flushed to the new pgdat and > hence the wrong node, not the one cached in obj_stock. It would be great to explicitly mention user observable problems here. I do assume this will make slab stats skewed but the effect wouldn't be very big, right? > Fix that by flushing the data to the cached pgdat instead. > > Fixes: 68ac5b3c8db2 ("mm/memcg: cache vmstat data in percpu memcg_stock_pcp") > Signed-off-by: Waiman Long Acked-by: Michal Hocko > --- > mm/memcontrol.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index ae1f5d0cb581..881ec4ddddcd 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -3106,17 +3106,19 @@ void mod_objcg_state(struct obj_cgroup *objcg, struct pglist_data *pgdat, > stock->cached_pgdat = pgdat; > } else if (stock->cached_pgdat != pgdat) { > /* Flush the existing cached vmstat data */ > + struct pglist_data *oldpg = stock->cached_pgdat; > + > + stock->cached_pgdat = pgdat; > if (stock->nr_slab_reclaimable_b) { > - mod_objcg_mlstate(objcg, pgdat, NR_SLAB_RECLAIMABLE_B, > + mod_objcg_mlstate(objcg, oldpg, NR_SLAB_RECLAIMABLE_B, > stock->nr_slab_reclaimable_b); > stock->nr_slab_reclaimable_b = 0; > } > if (stock->nr_slab_unreclaimable_b) { > - mod_objcg_mlstate(objcg, pgdat, NR_SLAB_UNRECLAIMABLE_B, > + mod_objcg_mlstate(objcg, oldpg, NR_SLAB_UNRECLAIMABLE_B, > stock->nr_slab_unreclaimable_b); > stock->nr_slab_unreclaimable_b = 0; > } > - stock->cached_pgdat = pgdat; Minor nit. Is there any reason to move the cached_pgdat? TBH I found the original way better from the readability POV. > } > > bytes = (idx == NR_SLAB_RECLAIMABLE_B) ? &stock->nr_slab_reclaimable_b > -- > 2.18.1 -- Michal Hocko SUSE Labs