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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 9200DEC01B6 for ; Mon, 23 Mar 2026 09:47:55 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 056B76B0005; Mon, 23 Mar 2026 05:47:55 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0070E6B0089; Mon, 23 Mar 2026 05:47:54 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E38656B008A; Mon, 23 Mar 2026 05:47:54 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id CDBB36B0005 for ; Mon, 23 Mar 2026 05:47:54 -0400 (EDT) Received: from smtpin25.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 97306160A9E for ; Mon, 23 Mar 2026 09:47:54 +0000 (UTC) X-FDA: 84576851268.25.1701024 Received: from out-178.mta0.migadu.com (out-178.mta0.migadu.com [91.218.175.178]) by imf09.hostedemail.com (Postfix) with ESMTP id 9666F14000B for ; Mon, 23 Mar 2026 09:47:52 +0000 (UTC) Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=CwxYaQu1; spf=pass (imf09.hostedemail.com: domain of qi.zheng@linux.dev designates 91.218.175.178 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1774259273; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=hUcyey8JJET54dG1RcxlUPbktgzb/K1oah1AT7wcgO0=; b=4hEVhjuFBK8P8inbyiyV/5FiSkogOBZ9GD69dSYu2+/esQTk7X1Z1TF5Te70bgj+G4EEcz BRBhF4hZHh/CNVCRJ2z4/Y0UfNujbJJYgfKE0u0XSIBC6unmSaD7UU95cC28h+qy+4F+V/ g9TmPbSeQLyxNihZul2sKI4mMQR4cLo= ARC-Authentication-Results: i=1; imf09.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=CwxYaQu1; spf=pass (imf09.hostedemail.com: domain of qi.zheng@linux.dev designates 91.218.175.178 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1774259273; a=rsa-sha256; cv=none; b=z3frpPe1YpVwtU8W6aad/K20S+lEFgYZD3RuP3EYCiO8nz0KSoDGqGeVc+Y2oE+dJ22OAu DeUot+mTX1cg1JbNmnhTiiIyl9zj59yOupkgHcZGfZugVkICqoTq8DDWEQjVsTkHr9TQEu ilMDTyQIRtWw82qRjN+Q/7A2mPCKUjA= Message-ID: <2d39ea5e-fd69-4acf-8518-a504f5f7a838@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1774259270; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=hUcyey8JJET54dG1RcxlUPbktgzb/K1oah1AT7wcgO0=; b=CwxYaQu1n0VmMyb46AU0irJsJRHETzAAsRr3dEl7G8MuKiYiMDYJxB7bCYjztd8Wlyol9Q tvBYS+JsyWstB+h4ToehfXaGvY8XOajahWwp21Dsd6zJj1Oxi8+TUoErpvCTE9LFK/ko7E qunY8dUK2nRfmD6DFG1q6p5QnH6u9h4= Date: Mon, 23 Mar 2026 17:47:27 +0800 MIME-Version: 1.0 Subject: Re: [PATCH v6 30/33] mm: memcontrol: prepare for reparenting non-hierarchical stats To: "Harry Yoo (Oracle)" Cc: hannes@cmpxchg.org, hughd@google.com, mhocko@suse.com, roman.gushchin@linux.dev, shakeel.butt@linux.dev, muchun.song@linux.dev, david@kernel.org, lorenzo.stoakes@oracle.com, ziy@nvidia.com, harry.yoo@oracle.com, yosry.ahmed@linux.dev, imran.f.khan@oracle.com, kamalesh.babulal@oracle.com, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, chenridong@huaweicloud.com, mkoutny@suse.com, akpm@linux-foundation.org, hamzamahfooz@linux.microsoft.com, apais@linux.microsoft.com, lance.yang@linux.dev, bhe@redhat.com, usamaarif642@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Qi Zheng , Yosry Ahmed References: X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Qi Zheng In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT X-Stat-Signature: wnk8axapkct1yr5upwnk3mskywekemtt X-Rspamd-Server: rspam09 X-Rspam-User: X-Rspamd-Queue-Id: 9666F14000B X-HE-Tag: 1774259272-223201 X-HE-Meta: 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 S/DNyNi9 mCzJmcTzAZWAaGKI/zyIMVpoe3Gi2ybdb7mm/JVqWGvUCzpkqGZJ/EqOTKQrfepVOWrvG+H6M1t9KMtNtrmX+X+KaRA2+cEX66w6dALqkwQibNXW9pi31P80HB4lrm2/ApAta63CZlEygXw9kBbyrmdRdDXDk0udMKolQq7tOvRslXTqSTWBXCj4oOGt8/3gSL6kflmUjOd/hFQnbhckfxRUqQHRqDLSSkHuU1o5xLGjwFleXaLBSXlf+aB6fOeh+wKZO Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Harry, On 3/23/26 3:53 PM, Harry Yoo (Oracle) wrote: > On Thu, Mar 05, 2026 at 07:52:48PM +0800, Qi Zheng wrote: >> From: Qi Zheng >> >> To resolve the dying memcg issue, we need to reparent LRU folios of child >> memcg to its parent memcg. This could cause problems for non-hierarchical >> stats. >> >> As Yosry Ahmed pointed out: >> >> ``` >> In short, if memory is charged to a dying cgroup at the time of >> reparenting, when the memory gets uncharged the stats updates will occur >> at the parent. This will update both hierarchical and non-hierarchical >> stats of the parent, which would corrupt the parent's non-hierarchical >> stats (because those counters were never incremented when the memory was >> charged). >> ``` >> >> Now we have the following two types of non-hierarchical stats, and they >> are only used in CONFIG_MEMCG_V1: >> >> a. memcg->vmstats->state_local[i] >> b. pn->lruvec_stats->state_local[i] >> >> To ensure that these non-hierarchical stats work properly, we need to >> reparent these non-hierarchical stats after reparenting LRU folios. To >> this end, this commit makes the following preparations: >> >> 1. implement reparent_state_local() to reparent non-hierarchical stats >> 2. make css_killed_work_fn() to be called in rcu work, and implement >> get_non_dying_memcg_start() and get_non_dying_memcg_end() to avoid race >> between mod_memcg_state()/mod_memcg_lruvec_state() >> and reparent_state_local() >> >> Co-developed-by: Yosry Ahmed >> Signed-off-by: Yosry Ahmed >> Signed-off-by: Qi Zheng >> Acked-by: Shakeel Butt >> --- >> kernel/cgroup/cgroup.c | 9 ++-- >> mm/memcontrol-v1.c | 16 +++++++ >> mm/memcontrol-v1.h | 7 +++ >> mm/memcontrol.c | 97 ++++++++++++++++++++++++++++++++++++++++++ >> 4 files changed, 125 insertions(+), 4 deletions(-) >> >> diff --git a/mm/memcontrol.c b/mm/memcontrol.c >> index 23b70bd80ddc9..b0519a16f5684 100644 >> --- a/mm/memcontrol.c >> +++ b/mm/memcontrol.c >> @@ -473,6 +501,30 @@ unsigned long lruvec_page_state_local(struct lruvec *lruvec, >> return x; >> } >> >> +#ifdef CONFIG_MEMCG_V1 >> +static void __mod_memcg_lruvec_state(struct mem_cgroup_per_node *pn, >> + enum node_stat_item idx, int val); >> + >> +void reparent_memcg_lruvec_state_local(struct mem_cgroup *memcg, >> + struct mem_cgroup *parent, int idx) >> +{ >> + int nid; >> + >> + for_each_node(nid) { >> + struct lruvec *child_lruvec = mem_cgroup_lruvec(memcg, NODE_DATA(nid)); >> + struct lruvec *parent_lruvec = mem_cgroup_lruvec(parent, NODE_DATA(nid)); >> + unsigned long value = lruvec_page_state_local(child_lruvec, idx); >> + struct mem_cgroup_per_node *child_pn, *parent_pn; >> + >> + child_pn = container_of(child_lruvec, struct mem_cgroup_per_node, lruvec); >> + parent_pn = container_of(parent_lruvec, struct mem_cgroup_per_node, lruvec); >> + >> + __mod_memcg_lruvec_state(child_pn, idx, -value); >> + __mod_memcg_lruvec_state(parent_pn, idx, value); > > We should probably change the type of `@val` from int to val to avoid > losing non hierarchical stats during reparenting? The parameter and return value of memcg_state_val_in_pages() are both of type int, so perhaps we need a cleanup patch to do this? I will send a cleanup patchset to do this, which includes the following: https://lore.kernel.org/all/5e178b4e-a9e0-44dc-a18d-8c014365ee2f@linux.dev/ Thanks, Qi >