From mboxrd@z Thu Jan 1 00:00:00 1970 From: 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> References: <20230411133601.2969636-1-longman@redhat.com> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: 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= In-Reply-To: <20230411133601.2969636-1-longman@redhat.com> List-ID: Content-Type: text/plain; charset="us-ascii" 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 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; + /* + * 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, struct kernel_clone_args *kargs) return ret; do_each_subsys_mask(ss, i, have_canfork_callback) { + if (ss->clone_into_cgroup_can_fork && + !(kargs->flags & CLONE_INTO_CGROUP)) + continue; + ret = ss->can_fork(child, kargs->cset); if (ret) goto out_revert; @@ -6528,8 +6532,12 @@ int cgroup_can_fork(struct task_struct *child, struct kernel_clone_args *kargs) for_each_subsys(ss, j) { if (j >= 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); } cgroup_css_set_put_fork(kargs); @@ -6552,9 +6560,14 @@ void cgroup_cancel_fork(struct task_struct *child, struct cgroup_subsys *ss; int i; - 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); + } 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 = { .dfl_cftypes = dfl_files, .early_init = true, .threaded = true, + .clone_into_cgroup_can_fork = true, }; /** -- 2.31.1