From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-172.mta0.migadu.com (out-172.mta0.migadu.com [91.218.175.172]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 98D0023E25B for ; Tue, 24 Mar 2026 04:25:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774326353; cv=none; b=WiglhilaM+9yDxOYSNJp9L+5iXt6QHoj5bpToQ0PWITTbSZOXo7eEoRR0N+1zcaXLgwDAwRSKP6nEBURtP2BMiJXt1sBFGOlMEu6KIQcSE8nP2yBab5jCz5sS2K+A4q8TIs/51gbKCra3M1gA/uqdvy5j4Hqc12iuAUYjTcnAAw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774326353; c=relaxed/simple; bh=YjMp53OKfadWj+kNw02JjPxJqovKUYQQe19iaJSbxKM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=QDT3B8ypNuBKHbntSnMtM5/Lrpd2CxG0KJcXGWHCQwVGMSsnLDXRqK3g89LDpTRFdI5WBMi3dzZRA1MIaMOaCxvTHJZsP8TFS/io4QcOoYa2fBYSwjLZf9ftjgyPyycZYy1weX7q2Z3g3aEqiooizM3xNd7J2z5xsfDH55dahaI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=VCisPo8C; arc=none smtp.client-ip=91.218.175.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="VCisPo8C" Message-ID: <138d9363-ab0c-4f5c-bedc-b326f5aaee91@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1774326339; 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=xFm4rq63hk/RC8ec4idA1Wj6bRsPq9bmm+kOdtLr6mE=; b=VCisPo8Co7n3knIGM0A0ZVk9KeDhkyF3dYJNyIngSsxp5cgCjpBS2vBIAqIineGlMW265t Uq314LeejaqmyZiE6GvJye2uYRmVqRhgEWRLaTivnDDhugIdiI4luxhrqq66i5SUKZiMwj nIUZDYgdo3d05U+icbURkSf2M1LGkwo= Date: Tue, 24 Mar 2026 12:25:16 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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, Yosry Ahmed , Qi Zheng References: <2d39ea5e-fd69-4acf-8518-a504f5f7a838@linux.dev> 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 On 3/24/26 12:05 PM, Harry Yoo (Oracle) wrote: > On Tue, Mar 24, 2026 at 10:54:48AM +0800, Qi Zheng wrote: >> On 3/23/26 8:25 PM, Harry Yoo (Oracle) wrote: >>> On Mon, Mar 23, 2026 at 05:47:27PM +0800, Qi Zheng wrote: >>>> On 3/23/26 3:53 PM, Harry Yoo (Oracle) wrote: >>>>> On Thu, Mar 05, 2026 at 07:52:48PM +0800, Qi Zheng wrote: >>>>>> 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? >>> >>> Yes! >>> >>> and @val in memcg_rstat_updated() too, I think. >> >> Right. >> >>> >>>> 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! >>> >>> Should that ideally be applied before this patchset? >> >> This would conflict with the current patchset. > > Right. > >> The v6 has been in mm-unstable for some time > > Right. > >> so I prefer to add a cleanup patchset to >> avoid interfering with the merge of this patchset. > > but it's a little bit more than a cleanup, no? > > I'd say without the followup, this patchset introduces a very subtle > (likely nobody would notice) functional regression visible on memcgs > with billions of pages. Right. > >> Otherwise, sending v7 might be more appropriate. > > I think it should be sent either as v7 or as part of v7.1-rcX. > (Whichever way Andrew prefers) OK, In any case I will first send out the cleanup/fix patchset for everyone to review. Thanks, Qi >