From nobody Tue Feb 10 23:01:41 2026 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 3A7A8C76196 for ; Tue, 11 Apr 2023 13:37:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230104AbjDKNhU (ORCPT ); Tue, 11 Apr 2023 09:37:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46486 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229661AbjDKNhK (ORCPT ); Tue, 11 Apr 2023 09:37:10 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E31013A91 for ; Tue, 11 Apr 2023 06:36:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1681220184; 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=xK1NCjqBm+Noko8JAoUQYHl2QqweOko54B+7fb/aUQk=; b=Qpxux3t/jAPWs4Z4I5FiIbMArm5L0WPre2d47TWcyiXHkFnejqb5LqvnKltjcbhs0uwdMD rkC6z7U/OvaiBaJtPLoCx+wmwKCjk2G6wmSXhMosESarQ7LtqFLh9W1099VBSlV9CaLGeR 3TbgpsAG2qfqvpBZxwakK9GGt9NqOxs= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-613-DwDKLdOJOFO6fjaq4KMiHg-1; Tue, 11 Apr 2023 09:36:21 -0400 X-MC-Unique: DwDKLdOJOFO6fjaq4KMiHg-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 78B611C0878A; Tue, 11 Apr 2023 13:36:20 +0000 (UTC) Received: from llong.com (unknown [10.22.33.155]) by smtp.corp.redhat.com (Postfix) with ESMTP id 09FBA47CD0; Tue, 11 Apr 2023 13:36:20 +0000 (UTC) From: Waiman Long To: Tejun Heo , Zefan Li , Johannes Weiner , Christian Brauner Cc: cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Juri Lelli , Dietmar Eggemann , =?UTF-8?q?Michal=20Koutn=C3=BD?= , Giuseppe Scrivano , Waiman Long Subject: [PATCH v4 5/5] cgroup/cpuset: Optimize out unneeded cpuset_can_fork/cpuset_cancel_fork calls Date: Tue, 11 Apr 2023 09:36:01 -0400 Message-Id: <20230411133601.2969636-6-longman@redhat.com> In-Reply-To: <20230411133601.2969636-1-longman@redhat.com> References: <20230411133601.2969636-1-longman@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.5 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" The newly introduced cpuset_can_fork() and cpuset_cancel_fork() calls are only needed when the CLONE_INTO_CGROUP flag is set which is not likely. Adding an extra cpuset_can_fork() call does introduce a bit of performance overhead in the fork/clone fastpath. To reduce this performance overhead, introduce a new clone_into_cgroup_can_fork flag into the cgroup_subsys structure. This flag, when set, will call the can_fork and cancel_fork methods only if the CLONE_INTO_CGROUP flag is set. The cpuset code is now modified to set this flag. The same cpuset checking code in cpuset_can_fork() and cpuset_cancel_fork() will have to stay as the cgroups can be different, but the cpusets may still be the same. So the same check must be present in both cpuset_fork() and cpuset_can_fork() to make sure that attach_in_progress is correctly set. Signed-off-by: Waiman Long --- include/linux/cgroup-defs.h | 6 ++++++ kernel/cgroup/cgroup.c | 23 ++++++++++++++++++----- kernel/cgroup/cpuset.c | 1 + 3 files changed, 25 insertions(+), 5 deletions(-) diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h index 8a0d5466c7be..0087a47d80a2 100644 --- a/include/linux/cgroup-defs.h +++ b/include/linux/cgroup-defs.h @@ -701,6 +701,12 @@ struct cgroup_subsys { */ bool threaded:1; =20 + /* + * If %true, the controller will call can_fork and cancel_fork + * methods only if CLONE_INTO_CGROUP flag is set. + */ + bool clone_into_cgroup_can_fork:1; + /* the following two fields are initialized automatically during boot */ int id; const char *name; diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 83ea13f2ccb1..23701e959ef5 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -6517,6 +6517,10 @@ int cgroup_can_fork(struct task_struct *child, struc= t kernel_clone_args *kargs) return ret; =20 do_each_subsys_mask(ss, i, have_canfork_callback) { + if (ss->clone_into_cgroup_can_fork && + !(kargs->flags & CLONE_INTO_CGROUP)) + continue; + ret =3D ss->can_fork(child, kargs->cset); if (ret) goto out_revert; @@ -6528,8 +6532,12 @@ int cgroup_can_fork(struct task_struct *child, struc= t kernel_clone_args *kargs) for_each_subsys(ss, j) { if (j >=3D i) break; - if (ss->cancel_fork) - ss->cancel_fork(child, kargs->cset); + if (!ss->cancel_fork || + (ss->clone_into_cgroup_can_fork && + !(kargs->flags & CLONE_INTO_CGROUP))) + continue; + + ss->cancel_fork(child, kargs->cset); } =20 cgroup_css_set_put_fork(kargs); @@ -6552,9 +6560,14 @@ void cgroup_cancel_fork(struct task_struct *child, struct cgroup_subsys *ss; int i; =20 - for_each_subsys(ss, i) - if (ss->cancel_fork) - ss->cancel_fork(child, kargs->cset); + for_each_subsys(ss, i) { + if (!ss->cancel_fork || + (ss->clone_into_cgroup_can_fork && + !(kargs->flags & CLONE_INTO_CGROUP))) + continue; + + ss->cancel_fork(child, kargs->cset); + } =20 cgroup_css_set_put_fork(kargs); } diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index e4ca2dd2b764..937ef4d60cd4 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -3391,6 +3391,7 @@ struct cgroup_subsys cpuset_cgrp_subsys =3D { .dfl_cftypes =3D dfl_files, .early_init =3D true, .threaded =3D true, + .clone_into_cgroup_can_fork =3D true, }; =20 /** --=20 2.31.1