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 6E49ED4A5EB for ; Mon, 19 Jan 2026 03:35:08 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 4D67F6B00F2; Sun, 18 Jan 2026 22:35:07 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 4840A6B00F3; Sun, 18 Jan 2026 22:35:07 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3617A6B00F4; Sun, 18 Jan 2026 22:35:07 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 1F96F6B00F2 for ; Sun, 18 Jan 2026 22:35:07 -0500 (EST) Received: from smtpin16.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 8FB2EBA50B for ; Mon, 19 Jan 2026 03:35:06 +0000 (UTC) X-FDA: 84347297412.16.50A8A71 Received: from out-170.mta0.migadu.com (out-170.mta0.migadu.com [91.218.175.170]) by imf10.hostedemail.com (Postfix) with ESMTP id D89E0C0003 for ; Mon, 19 Jan 2026 03:35:04 +0000 (UTC) Authentication-Results: imf10.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=iPpPBLFj; spf=pass (imf10.hostedemail.com: domain of qi.zheng@linux.dev designates 91.218.175.170 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=1768793705; 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=A2DwTuePUycHQ/sZnpKkhBxd7ANgEf/6qnp7jSSdIz0=; b=L1XsgHCymTVIPDvKceLbS72mNZI5syooVRn6KaCMTeT95vXwyZIoPOAYLw7MexXX/hzvV6 j8cFIZ06zQxtnmXVD0gau0t1SNvKESOrDo1dBCumbNq057CyJIhnX2NcQ0RRIXlwaHkhfu yeVI4/s+kekpmglyHqwifdnKZ7YDH9U= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1768793705; a=rsa-sha256; cv=none; b=IcUNwyB9H7y2he3T4hy/SMZY4F4JoH+BHmZ2ARWYODUT0Pc2oOPGJP33dcSNyy+8YPOzZg Nyn3z3MPnWyS2qsGJuaxnIQ2pSQzHTCGVKpQzBOMD+cAiaQDyU44I7aub1M1AEJrYoLTAU ABoQsN7sofm6Vo3TPHO8hn1bDF8Wks4= ARC-Authentication-Results: i=1; imf10.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=iPpPBLFj; spf=pass (imf10.hostedemail.com: domain of qi.zheng@linux.dev designates 91.218.175.170 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev; dmarc=pass (policy=none) header.from=linux.dev Message-ID: <9b9057f8-4c4c-4067-b6ba-0791888c25e8@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1768793702; 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=A2DwTuePUycHQ/sZnpKkhBxd7ANgEf/6qnp7jSSdIz0=; b=iPpPBLFjReNZJL6MQN0s8qLiVxa2/AWyFPmjz8D9Gb1HpGV0B9CiYg2GxYgDkoDu1QUDHl FvZzGD9XHP/jh3U68r/UuLZcezwR0fcWjyFUX24Ik9X00TdTOjw7ZPW4LKkx/5kbHk3NSI rEL74nvf/6sh8rpkScJFwmMkO7xgF2M= Date: Mon, 19 Jan 2026 11:34:53 +0800 MIME-Version: 1.0 Subject: Re: [PATCH v3 28/30] mm: memcontrol: prepare for reparenting state_local To: Shakeel Butt Cc: 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, 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-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: D89E0C0003 X-Rspam-User: X-Stat-Signature: d4pneiicgqruquf9waw5kq79ph7qf4ci X-HE-Tag: 1768793704-476920 X-HE-Meta: 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 1/18/26 11:20 AM, Shakeel Butt wrote: > On Wed, Jan 14, 2026 at 07:32:55PM +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. The following counts are all non-hierarchical >> and need to be reparented to prevent the counts of parent memcg overflow. >> >> 1. memcg->vmstats->state_local[i] >> 2. pn->lruvec_stats->state_local[i] >> >> This commit implements the specific function, which will be used during >> the reparenting process. > > Please add more explanation which was discussed in the email chain at > https://lore.kernel.org/all/5dsb6q2r4xsi24kk5gcnckljuvgvvp6nwifwvc4wuho5hsifeg@5ukg2dq6ini5/ OK, will do. > > Also move the upward traversal code in mod_memcg_state() and > mod_memcg_lruvec_state() you added in later patch to this patch and make > it under CONFIG_MEMCG_V1. > > Something like: > > #ifdef CONFIG_MEMCG_V1 > while (memcg_is_dying(memcg)) > memcg = parent_mem_cgroup(memcg); > #endif OK, will do. > > >> >> Signed-off-by: Qi Zheng >> --- >> include/linux/memcontrol.h | 4 +++ >> mm/memcontrol-v1.c | 16 +++++++++++ >> mm/memcontrol-v1.h | 3 ++ >> mm/memcontrol.c | 56 ++++++++++++++++++++++++++++++++++++++ >> 4 files changed, 79 insertions(+) >> >> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h >> index 26c3c0e375f58..f84a23f13ffb4 100644 >> --- a/include/linux/memcontrol.h >> +++ b/include/linux/memcontrol.h >> @@ -963,12 +963,16 @@ static inline void mod_memcg_page_state(struct page *page, >> >> unsigned long memcg_events(struct mem_cgroup *memcg, int event); >> unsigned long memcg_page_state(struct mem_cgroup *memcg, int idx); >> +void reparent_memcg_state_local(struct mem_cgroup *memcg, >> + struct mem_cgroup *parent, int idx); >> unsigned long memcg_page_state_output(struct mem_cgroup *memcg, int item); >> bool memcg_stat_item_valid(int idx); >> bool memcg_vm_event_item_valid(enum vm_event_item idx); >> unsigned long lruvec_page_state(struct lruvec *lruvec, enum node_stat_item idx); >> unsigned long lruvec_page_state_local(struct lruvec *lruvec, >> enum node_stat_item idx); >> +void reparent_memcg_lruvec_state_local(struct mem_cgroup *memcg, >> + struct mem_cgroup *parent, int idx); >> >> void mem_cgroup_flush_stats(struct mem_cgroup *memcg); >> void mem_cgroup_flush_stats_ratelimited(struct mem_cgroup *memcg); >> diff --git a/mm/memcontrol-v1.c b/mm/memcontrol-v1.c >> index f0ef650d2317b..800606135e7ba 100644 >> --- a/mm/memcontrol-v1.c >> +++ b/mm/memcontrol-v1.c >> @@ -1898,6 +1898,22 @@ static const unsigned int memcg1_events[] = { >> PGMAJFAULT, >> }; >> >> +void reparent_memcg1_state_local(struct mem_cgroup *memcg, struct mem_cgroup *parent) >> +{ >> + int i; >> + >> + for (i = 0; i < ARRAY_SIZE(memcg1_stats); i++) >> + reparent_memcg_state_local(memcg, parent, memcg1_stats[i]); >> +} >> + >> +void reparent_memcg1_lruvec_state_local(struct mem_cgroup *memcg, struct mem_cgroup *parent) >> +{ >> + int i; >> + >> + for (i = 0; i < ARRAY_SIZE(memcg1_stats); i++) >> + reparent_memcg_lruvec_state_local(memcg, parent, memcg1_stats[i]); >> +} >> + >> void memcg1_stat_format(struct mem_cgroup *memcg, struct seq_buf *s) >> { >> unsigned long memory, memsw; >> diff --git a/mm/memcontrol-v1.h b/mm/memcontrol-v1.h >> index eb3c3c1056574..45528195d3578 100644 >> --- a/mm/memcontrol-v1.h >> +++ b/mm/memcontrol-v1.h >> @@ -41,6 +41,7 @@ static inline bool do_memsw_account(void) >> >> unsigned long memcg_events_local(struct mem_cgroup *memcg, int event); >> unsigned long memcg_page_state_local(struct mem_cgroup *memcg, int idx); >> +void mod_memcg_page_state_local(struct mem_cgroup *memcg, int idx, unsigned long val); >> unsigned long memcg_page_state_local_output(struct mem_cgroup *memcg, int item); >> bool memcg1_alloc_events(struct mem_cgroup *memcg); >> void memcg1_free_events(struct mem_cgroup *memcg); >> @@ -73,6 +74,8 @@ void memcg1_uncharge_batch(struct mem_cgroup *memcg, unsigned long pgpgout, >> unsigned long nr_memory, int nid); >> >> void memcg1_stat_format(struct mem_cgroup *memcg, struct seq_buf *s); >> +void reparent_memcg1_state_local(struct mem_cgroup *memcg, struct mem_cgroup *parent); >> +void reparent_memcg1_lruvec_state_local(struct mem_cgroup *memcg, struct mem_cgroup *parent); >> >> void memcg1_account_kmem(struct mem_cgroup *memcg, int nr_pages); >> static inline bool memcg1_tcpmem_active(struct mem_cgroup *memcg) >> diff --git a/mm/memcontrol.c b/mm/memcontrol.c >> index 70583394f421f..7aa32b97c9f17 100644 >> --- a/mm/memcontrol.c >> +++ b/mm/memcontrol.c >> @@ -225,6 +225,28 @@ static inline struct obj_cgroup *__memcg_reparent_objcgs(struct mem_cgroup *memc >> return objcg; >> } >> >> +#ifdef CONFIG_MEMCG_V1 >> +static void __mem_cgroup_flush_stats(struct mem_cgroup *memcg, bool force); >> + >> +static inline void reparent_state_local(struct mem_cgroup *memcg, struct mem_cgroup *parent) >> +{ >> + if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) >> + return; >> + >> + synchronize_rcu(); > > Hmm synchrinuze_rcu() is a heavy hammer here. Also you would need rcu > read lock in mod_memcg_state() & mod_memcg_lruvec_state() for this > synchronize_rcu(). Since these two functions require memcg or lruvec, they are already within the critical section of the RCU lock. > > Hmm instead of synchronize_rcu() here, we can use queue_rcu_work() in > css_killed_ref_fn(). It would be as simple as the following: It does look much simpler, will do. Thanks, Qi > > diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c > index e717208cfb18..549a8e026194 100644 > --- a/kernel/cgroup/cgroup.c > +++ b/kernel/cgroup/cgroup.c > @@ -6046,8 +6046,8 @@ int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name, umode_t mode) > */ > static void css_killed_work_fn(struct work_struct *work) > { > - struct cgroup_subsys_state *css = > - container_of(work, struct cgroup_subsys_state, destroy_work); > + struct cgroup_subsys_state *css = container_of(to_rcu_work(work), > + struct cgroup_subsys_state, destroy_rwork); > > cgroup_lock(); > > @@ -6068,8 +6068,8 @@ static void css_killed_ref_fn(struct percpu_ref *ref) > container_of(ref, struct cgroup_subsys_state, refcnt); > > if (atomic_dec_and_test(&css->online_cnt)) { > - INIT_WORK(&css->destroy_work, css_killed_work_fn); > - queue_work(cgroup_offline_wq, &css->destroy_work); > + INIT_RCU_WORK(&css->destroy_rwork, css_killed_work_fn); > + queue_rcu_work(cgroup_offline_wq, &css->destroy_rwork); > } > } > >> + >> + __mem_cgroup_flush_stats(memcg, true); >> + >> + /* The following counts are all non-hierarchical and need to be reparented. */ >> + reparent_memcg1_state_local(memcg, parent); >> + reparent_memcg1_lruvec_state_local(memcg, parent); >> +} >> +#else >> +static inline void reparent_state_local(struct mem_cgroup *memcg, struct mem_cgroup *parent) >> +{ >> +} >> +#endif >> +