From nobody Tue Dec 16 15:35:48 2025 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A58BEE728D6 for ; Fri, 29 Sep 2023 18:01:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232748AbjI2SBg (ORCPT ); Fri, 29 Sep 2023 14:01:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49158 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233764AbjI2SB0 (ORCPT ); Fri, 29 Sep 2023 14:01:26 -0400 Received: from out-199.mta0.migadu.com (out-199.mta0.migadu.com [91.218.175.199]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AEE4A1B4 for ; Fri, 29 Sep 2023 11:01:24 -0700 (PDT) X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1696010482; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=QxcU5o8Zg0M6jb420o2zIxJRSsKU6LzkAHBX3GqSFms=; b=ImdhAu3ALKSdHrgwpMCUhyBJ4W47XhCUnKHwtUs8l/RzPj6hc/NfPFnlbT6TZr/umtTkJh xhHHggDB8z5vJqFJ1wexSJW0oPmubHVLru/4OppYheK+YhIChrW1Atc7eG+tLhXmZpg8Xt CFlnH7b6YjSVLnA1ud3LguQ/xHfr6LM= From: Roman Gushchin To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Johannes Weiner , Michal Hocko , Shakeel Butt , Muchun Song , Dennis Zhou , Andrew Morton , David Rientjes , Vlastimil Babka , Roman Gushchin Subject: [PATCH v1 3/5] mm: kmem: make memcg keep a reference to the original objcg Date: Fri, 29 Sep 2023 11:00:53 -0700 Message-ID: <20230929180056.1122002-4-roman.gushchin@linux.dev> In-Reply-To: <20230929180056.1122002-1-roman.gushchin@linux.dev> References: <20230929180056.1122002-1-roman.gushchin@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Migadu-Flow: FLOW_OUT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Keep a reference to the original objcg object for the entire life of a memcg structure. This allows to simplify the synchronization on the kernel memory allocation paths: pinning a (live) memcg will also pin the corresponding objcg. The memory overhead of this change is minimal because object cgroups usually outlive their corresponding memory cgroups even without this change, so it's only an additional pointer per memcg. Signed-off-by: Roman Gushchin (Cruise) --- include/linux/memcontrol.h | 8 +++++++- mm/memcontrol.c | 5 +++++ 2 files changed, 12 insertions(+), 1 deletion(-) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 1c1ebb269ac1..e59dea9d8666 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -299,7 +299,13 @@ struct mem_cgroup { =20 #ifdef CONFIG_MEMCG_KMEM int kmemcg_id; - struct obj_cgroup __rcu *objcg; + /* + * memcg->objcg is wiped out as a part of the objcg repaprenting + * process. memcg->orig_objcg preserves a pointer (and a reference) + * to the original objcg until the end of live of memcg. + */ + struct obj_cgroup __rcu *objcg; + struct obj_cgroup *orig_objcg; /* list of inherited objcgs, protected by objcg_lock */ struct list_head objcg_list; #endif diff --git a/mm/memcontrol.c b/mm/memcontrol.c index ec28f9cfc2f0..e9890f6e4da7 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -3803,6 +3803,8 @@ static int memcg_online_kmem(struct mem_cgroup *memcg) =20 objcg->memcg =3D memcg; rcu_assign_pointer(memcg->objcg, objcg); + obj_cgroup_get(objcg); + memcg->orig_objcg =3D objcg; =20 static_branch_enable(&memcg_kmem_online_key); =20 @@ -5297,6 +5299,9 @@ static void __mem_cgroup_free(struct mem_cgroup *memc= g) { int node; =20 + if (memcg->orig_objcg) + obj_cgroup_put(memcg->orig_objcg); + for_each_node(node) free_mem_cgroup_per_node_info(memcg, node); kfree(memcg->vmstats); --=20 2.42.0