From nobody Wed Dec 17 09:50:33 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 30B21CDB465 for ; Mon, 16 Oct 2023 22:19:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234277AbjJPWTi (ORCPT ); Mon, 16 Oct 2023 18:19:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57260 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234261AbjJPWTf (ORCPT ); Mon, 16 Oct 2023 18:19:35 -0400 Received: from out-205.mta1.migadu.com (out-205.mta1.migadu.com [IPv6:2001:41d0:203:375::cd]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4BD34EE for ; Mon, 16 Oct 2023 15:19:31 -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=1697494769; 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=8nbWMqlQbup8L2PuI3o6aZR+b1Gh4bcn04UHgRGHul4=; b=GVxjccE0wRDPf3xmRq5yp+EZpFthfbOTdOcitturXfYEyCKxOFwUAdjvcbfQaAHmjoiYHf XchZu3Jj3LIkIaTLAvXdaMbdYfKBOOd4vnoDv+0zus1yi0xwVi2DEtoTht+7fcm4V0ms/G FLHpSoYdp6Gpzdvw2ssI9g/dgNewT7w= From: Roman Gushchin To: Andrew Morton Cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Johannes Weiner , Michal Hocko , Shakeel@vger.kernel.org, Butt@vger.kernel.org, shakeelb@google.com, Muchun Song , Dennis Zhou , David Rientjes , Vlastimil Babka , Naresh Kamboju , Roman Gushchin Subject: [PATCH v3 3/5] mm: kmem: make memcg keep a reference to the original objcg Date: Mon, 16 Oct 2023 15:18:58 -0700 Message-ID: <20231016221900.4031141-4-roman.gushchin@linux.dev> In-Reply-To: <20231016221900.4031141-1-roman.gushchin@linux.dev> References: <20231016221900.4031141-1-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) Tested-by: Naresh Kamboju Acked-by: Shakeel Butt Reviewed-by: Vlastimil Babka --- 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 ab94ad4597d0..277690af383d 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 0605e45bd4a2..d90cc19e4113 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -3808,6 +3808,8 @@ 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 @@ -5302,6 +5304,9 @@ 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