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 DAA1BFD45FC for ; Thu, 26 Feb 2026 00:25:45 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 2CACB6B0088; Wed, 25 Feb 2026 19:25:45 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 278416B0089; Wed, 25 Feb 2026 19:25:45 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 15A586B008A; Wed, 25 Feb 2026 19:25:45 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 035E36B0088 for ; Wed, 25 Feb 2026 19:25:44 -0500 (EST) Received: from smtpin17.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id C120DB809B for ; Thu, 26 Feb 2026 00:25:44 +0000 (UTC) X-FDA: 84484714608.17.D990A9D Received: from out-189.mta1.migadu.com (out-189.mta1.migadu.com [95.215.58.189]) by imf24.hostedemail.com (Postfix) with ESMTP id 68EEF180002 for ; Thu, 26 Feb 2026 00:25:41 +0000 (UTC) Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=ey+g63E7; spf=pass (imf24.hostedemail.com: domain of shakeel.butt@linux.dev designates 95.215.58.189 as permitted sender) smtp.mailfrom=shakeel.butt@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=1772065543; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=yxPqJ6E7xvNtCuOu5zbMYJVgjaGYkAlt6qTcXlH4PpM=; b=wFdoaGqjAVO9N03lYiYeLSLpEtU5kg8ydaVbRXNbmNT1I4rZuRB7l7Y1O1mKeRpfNGu1JQ 68Om4u//3csFRPdFWm24frdnNV6r7jWYpBNJXL3BeH2EZPl0jQ4BFxZsSUSWSULtaWLCJm 0FdxXJ3uKJ44OzAx+qu6J0xDR4YkgYQ= ARC-Authentication-Results: i=1; imf24.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=ey+g63E7; spf=pass (imf24.hostedemail.com: domain of shakeel.butt@linux.dev designates 95.215.58.189 as permitted sender) smtp.mailfrom=shakeel.butt@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1772065543; a=rsa-sha256; cv=none; b=1mrVIiZbFThgIbFdq8KPRXvXpjK9XpbCE95mA8QPLj8XgR+V7HcEBfV8kheEc/l3FNuTom yR7Bze5jcvFBSD63kpANf9v+OK6GOqdoE3WGLGH7swZk1f2iNxib6zD1eYA0wI00eyA3kH xeLftw3r6/1pa3cwOP4fnGdSdecSiTg= Date: Wed, 25 Feb 2026 16:25:27 -0800 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1772065537; 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: in-reply-to:in-reply-to:references:references; bh=yxPqJ6E7xvNtCuOu5zbMYJVgjaGYkAlt6qTcXlH4PpM=; b=ey+g63E7MYcvKk29/8ZzUc3pXSq1elfr4bhlsqngJRjogeai6DH6S2T7UWhCrTJSC1+Bdt nyff4LdW470iaVY2rFfXfbEfQtnqRAZ/jH/mY6iGY/XJn1ZQO7iPw3GVDrGvpWDUTW+q5y 4uMIS9FVfmAwC2lXFCseF48lDsZ7Cy4= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Shakeel Butt To: Yosry Ahmed Cc: Qi Zheng , hannes@cmpxchg.org, hughd@google.com, mhocko@suse.com, roman.gushchin@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 Subject: Re: [PATCH v5 29/32] mm: memcontrol: prepare for reparenting non-hierarchical stats Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Queue-Id: 68EEF180002 X-Rspamd-Server: rspam02 X-Stat-Signature: hzupuaoea93mtr6wfdq5hiq8wpxmgktu X-HE-Tag: 1772065541-532296 X-HE-Meta: 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 xg2sPGiX Dl543rzPwCfHHNOzml1+n5DeqSaXJPDCECP451GVx5w9Wg53iGsVzvFoXLnGPk6AH12pqrimfGrC0j/IKhk2mnGSIN9tU/K4vNVJdW7b2qBp27Kl/ART/ot2Q1fBMvQuGnvsg29Y4v2XKXE5oPDo24PRKUmREtv39Jm4YpiTwbuQvoRh+EKWxb+bboc9NL/NhcCuBQ5NNZWVIOa+bhZLeIliNvw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Feb 25, 2026 at 06:58:59AM -0800, Yosry Ahmed wrote: > > @@ -473,6 +493,29 @@ unsigned long lruvec_page_state_local(struct lruvec *lruvec, > > return x; > > } > > > > +#ifdef CONFIG_MEMCG_V1 > > +void reparent_memcg_lruvec_state_local(struct mem_cgroup *memcg, > > + struct mem_cgroup *parent, int idx) > > +{ > > + int i = memcg_stats_index(idx); > > + int nid; > > + > > + if (WARN_ONCE(BAD_STAT_IDX(i), "%s: missing stat item %d\n", __func__, idx)) > > + return; > > + > > + 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)); > > + struct mem_cgroup_per_node *parent_pn; > > + unsigned long value = lruvec_page_state_local(child_lruvec, idx); > > + > > + parent_pn = container_of(parent_lruvec, struct mem_cgroup_per_node, lruvec); > > + > > + atomic_long_add(value, &(parent_pn->lruvec_stats->state_local[i])); > > + } > > +} > > Did you measure the impact of making state_local atomic on the flush > path? It's a slow path but we've seen pain from it being too slow > before, because it extends the critical section of the rstat flush > lock. Qi, please measure the impact on flushing and if no impact then no need to do anything as I don't want anymore churn in this series. > > Can we keep this non-atomic and use mod_memcg_lruvec_state() here? It > will update the stat on the local counter and it will be added to > state_local in the flush path when needed. We can even force another > flush in reparent_state_local () after reparenting is completed, if we > want to avoid leaving a potentially large stat update pending, as it > can be missed by mem_cgroup_flush_stats_ratelimited(). > > Same for reparent_memcg_state_local(), we can probably use mod_memcg_state()? Yosry, do you mind sending the patch you are thinking about over this series?