From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from dggsgout11.his.huawei.com (dggsgout11.his.huawei.com [45.249.212.51]) (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 9D9EA247280; Thu, 25 Dec 2025 06:23:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.51 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766643831; cv=none; b=C74pgPQ2ZyYHpUqFw72ax2jjMe7qd7k+2qMQ8I9PO+1ZtYlsD+u+EJacXVGPxf427987/9N2u1zVRJRyzSwHJ4vcVEgZaFxERXxY3JUEwZY4IGMqUiNT8MzhSgstBcTWDVFyq0gijf0z3lW/JU35RgbB9kJ+kknADzqqXo2SPV4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766643831; c=relaxed/simple; bh=IfPk9vsLXIaezG+bYlzWKQdFSsp2ueV4zEnCnbLHWRg=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=V+yjY/vHUkOh6l4tIz8jufhQTxYORBtRHwW6yY5xKOIgijLq+G5N8/zeczPrb9/RjOlg8PbL5M4T9lPYjCJEOlecEnK2LITnP38CIZvE1LDh9+BidnKdoFw84nBN7GvSi2I1ooMPp7qSUwCjpp+YS6FACX2gD0MYNDC5BLp+Eok= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com; spf=none smtp.mailfrom=huaweicloud.com; arc=none smtp.client-ip=45.249.212.51 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=huaweicloud.com Received: from mail.maildlp.com (unknown [172.19.163.198]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTPS id 4dcJZx0GPnzYQtGK; Thu, 25 Dec 2025 14:23:05 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.128]) by mail.maildlp.com (Postfix) with ESMTP id E20A440573; Thu, 25 Dec 2025 14:23:44 +0800 (CST) Received: from [10.67.111.176] (unknown [10.67.111.176]) by APP4 (Coremail) with SMTP id gCh0CgAn1vZv2Exp596fBQ--.65098S2; Thu, 25 Dec 2025 14:23:44 +0800 (CST) Message-ID: <644493f5-46df-45f7-a071-9ae7faae1f5c@huaweicloud.com> Date: Thu, 25 Dec 2025 14:23:42 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 06/28] mm: memcontrol: allocate object cgroup for non-kmem case To: Qi Zheng , 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, imran.f.khan@oracle.com, kamalesh.babulal@oracle.com, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, mkoutny@suse.com, akpm@linux-foundation.org, hamzamahfooz@linux.microsoft.com, apais@linux.microsoft.com, lance.yang@linux.dev Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Muchun Song , Qi Zheng References: <897be76398cb2027d08d1bcda05260ede54dc134.1765956025.git.zhengqi.arch@bytedance.com> Content-Language: en-US From: Chen Ridong In-Reply-To: <897be76398cb2027d08d1bcda05260ede54dc134.1765956025.git.zhengqi.arch@bytedance.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CM-TRANSID:gCh0CgAn1vZv2Exp596fBQ--.65098S2 X-Coremail-Antispam: 1UD129KBjvJXoW3Ary3CFyrJw4rGryfZF4kCrg_yoW7Ar1kpF sxGFy3Aw4rArWUGr1Ska9FvFyFka18XrW5K34xGw1xZrsIqw15tr12kw1UAFyrAFyfGr1x Jrs0yw1kGa1Yya7anT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUv0b4IE77IF4wAFF20E14v26ryj6rWUM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rwA2F7IY1VAKz4 vEj48ve4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_tr0E3s1l84ACjcxK6xIIjxv20xvEc7Cj xVAFwI0_Gr1j6F4UJwA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x 0267AKxVW0oVCq3wAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG 6I80ewAv7VC0I7IYx2IY67AKxVWUJVWUGwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFV Cjc4AY6r1j6r4UM4x0Y48IcVAKI48JM4IIrI8v6xkF7I0E8cxan2IY04v7MxkF7I0En4kS 14v26r4a6rW5MxAIw28IcxkI7VAKI48JMxC20s026xCaFVCjc4AY6r1j6r4UMI8I3I0E5I 8CrVAFwI0_Jr0_Jr4lx2IqxVCjr7xvwVAFwI0_JrI_JrWlx4CE17CEb7AF67AKxVW8ZVWr XwCIc40Y0x0EwIxGrwCI42IY6xIIjxv20xvE14v26r1j6r1xMIIF0xvE2Ix0cI8IcVCY1x 0267AKxVW8JVWxJwCI42IY6xAIw20EY4v20xvaj40_Jr0_JF4lIxAIcVC2z280aVAFwI0_ Jr0_Gr1lIxAIcVC2z280aVCY1x0267AKxVW8JVW8JrUvcSsGvfC2KfnxnUUI43ZEXa7IU0 s2-5UUUUU== X-CM-SenderInfo: hfkh02xlgr0w46kxt4xhlfz01xgou0bp/ On 2025/12/17 15:27, Qi Zheng wrote: > From: Muchun Song > > Pagecache pages are charged at allocation time and hold a reference > to the original memory cgroup until reclaimed. Depending on memory > pressure, page sharing patterns between different cgroups and cgroup > creation/destruction rates, many dying memory cgroups can be pinned > by pagecache pages, reducing page reclaim efficiency and wasting > memory. Converting LRU folios and most other raw memory cgroup pins > to the object cgroup direction can fix this long-living problem. > > As a result, the objcg infrastructure is no longer solely applicable > to the kmem case. In this patch, we extend the scope of the objcg > infrastructure beyond the kmem case, enabling LRU folios to reuse > it for folio charging purposes. > > It should be noted that LRU folios are not accounted for at the root > level, yet the folio->memcg_data points to the root_mem_cgroup. Hence, > the folio->memcg_data of LRU folios always points to a valid pointer. > However, the root_mem_cgroup does not possess an object cgroup. > Therefore, we also allocate an object cgroup for the root_mem_cgroup. > > Signed-off-by: Muchun Song > Signed-off-by: Qi Zheng > Reviewed-by: Harry Yoo > --- > mm/memcontrol.c | 51 +++++++++++++++++++++++-------------------------- > 1 file changed, 24 insertions(+), 27 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index ae234518d023c..544b3200db12d 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -204,10 +204,10 @@ static struct obj_cgroup *obj_cgroup_alloc(void) > return objcg; > } > > -static void memcg_reparent_objcgs(struct mem_cgroup *memcg, > - struct mem_cgroup *parent) > +static void memcg_reparent_objcgs(struct mem_cgroup *memcg) > { > struct obj_cgroup *objcg, *iter; > + struct mem_cgroup *parent = parent_mem_cgroup(memcg); > > objcg = rcu_replace_pointer(memcg->objcg, NULL, true); > > @@ -3294,30 +3294,17 @@ unsigned long mem_cgroup_usage(struct mem_cgroup *memcg, bool swap) > return val; > } > > -static int memcg_online_kmem(struct mem_cgroup *memcg) > +static void memcg_online_kmem(struct mem_cgroup *memcg) > { > - struct obj_cgroup *objcg; > - > if (mem_cgroup_kmem_disabled()) > - return 0; > + return; > > if (unlikely(mem_cgroup_is_root(memcg))) > - return 0; > - > - objcg = obj_cgroup_alloc(); > - if (!objcg) > - return -ENOMEM; > - > - objcg->memcg = memcg; > - rcu_assign_pointer(memcg->objcg, objcg); > - obj_cgroup_get(objcg); > - memcg->orig_objcg = objcg; > + return; > > static_branch_enable(&memcg_kmem_online_key); > Not about this patch. Should we add? if (!memcg_kmem_online()) static_branch_enable(&memcg_kmem_online_key); > memcg->kmemcg_id = memcg->id.id; > - > - return 0; > } > > static void memcg_offline_kmem(struct mem_cgroup *memcg) > @@ -3332,12 +3319,6 @@ static void memcg_offline_kmem(struct mem_cgroup *memcg) > > parent = parent_mem_cgroup(memcg); > memcg_reparent_list_lrus(memcg, parent); > - > - /* > - * Objcg's reparenting must be after list_lru's, make sure list_lru > - * helpers won't use parent's list_lru until child is drained. > - */ > - memcg_reparent_objcgs(memcg, parent); > } > > #ifdef CONFIG_CGROUP_WRITEBACK > @@ -3854,9 +3835,9 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css) > static int mem_cgroup_css_online(struct cgroup_subsys_state *css) > { > struct mem_cgroup *memcg = mem_cgroup_from_css(css); > + struct obj_cgroup *objcg; > > - if (memcg_online_kmem(memcg)) > - goto remove_id; > + memcg_online_kmem(memcg); > > /* > * A memcg must be visible for expand_shrinker_info() > @@ -3866,6 +3847,15 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state *css) > if (alloc_shrinker_info(memcg)) > goto offline_kmem; > > + objcg = obj_cgroup_alloc(); > + if (!objcg) > + goto free_shrinker; > + > + objcg->memcg = memcg; > + rcu_assign_pointer(memcg->objcg, objcg); > + obj_cgroup_get(objcg); > + memcg->orig_objcg = objcg; > + > if (unlikely(mem_cgroup_is_root(memcg)) && !mem_cgroup_disabled()) > queue_delayed_work(system_unbound_wq, &stats_flush_dwork, > FLUSH_TIME); > @@ -3888,9 +3878,10 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state *css) > xa_store(&mem_cgroup_ids, memcg->id.id, memcg, GFP_KERNEL); > > return 0; > +free_shrinker: > + free_shrinker_info(memcg); > offline_kmem: > memcg_offline_kmem(memcg); > -remove_id: > mem_cgroup_id_remove(memcg); > return -ENOMEM; > } > @@ -3908,6 +3899,12 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state *css) > > memcg_offline_kmem(memcg); > reparent_deferred_split_queue(memcg); > + /* > + * The reparenting of objcg must be after the reparenting of the > + * list_lru and deferred_split_queue above, which ensures that they will > + * not mistakenly get the parent list_lru and deferred_split_queue. > + */ > + memcg_reparent_objcgs(memcg); > reparent_shrinker_deferred(memcg); > wb_memcg_offline(memcg); > lru_gen_offline_memcg(memcg); Reviewed-by: Chen Ridong -- Best regards, Ridong