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From:   Chengming Zhou <zhouchengming@bytedance.com>
To:     tj@kernel.org, hannes@cmpxchg.org, mkoutny@suse.com,
        surenb@google.com
Cc:     gregkh@linuxfoundation.org, corbet@lwn.net, mingo@redhat.com,
        peterz@infradead.org, songmuchun@bytedance.com,
        cgroups@vger.kernel.org, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Chengming Zhou <zhouchengming@bytedance.com>
Subject: [PATCH v3 03/10] sched/psi: save percpu memory when !psi_cgroups_enabled
Date:   Wed, 24 Aug 2022 16:18:22 +0800
Message-Id: <20220824081829.33748-4-zhouchengming@bytedance.com>
In-Reply-To: <20220824081829.33748-1-zhouchengming@bytedance.com>
References: <20220824081829.33748-1-zhouchengming@bytedance.com>
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We won't use cgroup psi_group when !psi_cgroups_enabled, so don't
bother to alloc percpu memory and init for it.

Also don't need to migrate task PSI stats between cgroups in
cgroup_move_task().

Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
---
 kernel/sched/psi.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index 39463dcc16bb..77d53c03a76f 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -201,6 +201,7 @@ void __init psi_init(void)
 {
 	if (!psi_enable) {
 		static_branch_enable(&psi_disabled);
+		static_branch_disable(&psi_cgroups_enabled);
 		return;
 	}
 
@@ -950,7 +951,7 @@ void psi_memstall_leave(unsigned long *flags)
 #ifdef CONFIG_CGROUPS
 int psi_cgroup_alloc(struct cgroup *cgroup)
 {
-	if (static_branch_likely(&psi_disabled))
+	if (!static_branch_likely(&psi_cgroups_enabled))
 		return 0;
 
 	cgroup->psi = kzalloc(sizeof(struct psi_group), GFP_KERNEL);
@@ -968,7 +969,7 @@ int psi_cgroup_alloc(struct cgroup *cgroup)
 
 void psi_cgroup_free(struct cgroup *cgroup)
 {
-	if (static_branch_likely(&psi_disabled))
+	if (!static_branch_likely(&psi_cgroups_enabled))
 		return;
 
 	cancel_delayed_work_sync(&cgroup->psi->avgs_work);
@@ -996,7 +997,7 @@ void cgroup_move_task(struct task_struct *task, struct css_set *to)
 	struct rq_flags rf;
 	struct rq *rq;
 
-	if (static_branch_likely(&psi_disabled)) {
+	if (!static_branch_likely(&psi_cgroups_enabled)) {
 		/*
 		 * Lame to do this here, but the scheduler cannot be locked
 		 * from the outside, so we move cgroups from inside sched/.
-- 
2.37.2