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 207FDFD375D for ; Thu, 26 Feb 2026 06:42:01 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 31B3E6B008A; Thu, 26 Feb 2026 01:42:00 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 2C59B6B008C; Thu, 26 Feb 2026 01:42:00 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1D56A6B0092; Thu, 26 Feb 2026 01:42:00 -0500 (EST) 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 070FB6B008A for ; Thu, 26 Feb 2026 01:42:00 -0500 (EST) Received: from smtpin07.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 964521409E1 for ; Thu, 26 Feb 2026 06:41:59 +0000 (UTC) X-FDA: 84485662758.07.69AC68E Received: from out-185.mta0.migadu.com (out-185.mta0.migadu.com [91.218.175.185]) by imf14.hostedemail.com (Postfix) with ESMTP id B4C17100004 for ; Thu, 26 Feb 2026 06:41:57 +0000 (UTC) Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=GH10D8cg; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf14.hostedemail.com: domain of qi.zheng@linux.dev designates 91.218.175.185 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1772088118; a=rsa-sha256; cv=none; b=B/+Uo16ShUL/POmdpO6QmDwjRJJlDenoI1iGQF+Kx26lfOgSouEf0wArJim9CWjieIYmtd OND2lvpBJqaAaDfvKD1FG1hilIrLKbRoatwsUZwkTl8JXY3GEHrSrish36nwy/FbOYdr+G uQ6QurJe765r8qpmr/vpYxcQtTsOUm8= ARC-Authentication-Results: i=1; imf14.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=GH10D8cg; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf14.hostedemail.com: domain of qi.zheng@linux.dev designates 91.218.175.185 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1772088118; 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=tsoNYUIXRY4czYRyOTo1YFJNlOMgkydQUEar5VWPZRg=; b=vaRPzC+w5+c81BwDTmzR/DBcy9ktTyRcI2iGEc/0MsggbHMdZPzEa6fr1gS29AYsnmoGDQ ge4seTGGRMhaXMcg5STDuPwGsUaewwRNEppQ4zpaRTapDKEljZod0kPfwIfP62Lqz3lK/A PDCP2n9Uus/9G4L69cZFHGJQCs3P6N0= Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1772088115; 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=tsoNYUIXRY4czYRyOTo1YFJNlOMgkydQUEar5VWPZRg=; b=GH10D8cgG00SB31h6Il+LdJp6YDEXP7iGFxM0pnb/8gXr2wwfPQG+sYIw33iop0X5PIo1B +hcfWVme3JF8m61wizbiW6H/yAozr3BC0XTEKplh1nqIa774Bm7MRC6WZWnzjY3WhrTvAq i8y+roUbkTymN3mBUEnaPjT+YBppHeA= Date: Thu, 26 Feb 2026 14:41:28 +0800 MIME-Version: 1.0 Subject: Re: [PATCH v5 29/32] mm: memcontrol: prepare for reparenting non-hierarchical stats To: Yosry Ahmed 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 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: y384kxqh1bfjghqzo74himx4m1f4dehj X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: B4C17100004 X-HE-Tag: 1772088117-882609 X-HE-Meta: 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 LdSaIf15 LKqVTBN5ymbJtlX6XSOBk5u0rTO3GszTuoR8s/Z8BEP6dKpYSMal0nSCoukDa2eJk5pH1pRMTjFEArCHNGucTU/OYzJruvgWbsYfWua0gwK6RD59h9xpCET/z9EsKsx/AqVOlRP4HO+brWZVVNpN5m9WmPS5wXgN+LXSsYVK3yDQNy/GfrJhPEC4c7EngfD5RzEF8+uxe3oS161hHEOqf73FdeA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Yosry, On 2/25/26 10:58 PM, 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 No, because this is not a performance-critical path, I did not perform performance testing. :( > 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. Got it. Do you have any test cases that previously identified this problem? > > 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()? Thank you for providing optimization ideas; I will take a closer look.