>From b7be022bf811d02605098fa61b7545bc146b78e7 Mon Sep 17 00:00:00 2001 From: Tejun Heo <[email protected]> Date: Mon, 2 Apr 2018 14:45:20 -0700
cgroup_rstat_updated() ensures that the cgroup's rstat is linked to the parent. If there's no parent, it never gets linked and the function ends up grabbing and releasing the cgroup_rstat_lock each time for no reason which can be expensive. This hasn't been a problem till now because nobody was calling the function for the root cgroup but rstat is gonna be exposed to controllers and use cases, so let's get ready. Make cgroup_rstat_updated() an no-op for the root cgroup. Signed-off-by: Tejun Heo <[email protected]> --- Hello, This should address the scalability issue reported by kenrel test bot. All git branches updated accordingly. Thanks. kernel/cgroup/rstat.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c index 0d1d5fc..9a30b51 100644 --- a/kernel/cgroup/rstat.c +++ b/kernel/cgroup/rstat.c @@ -27,6 +27,10 @@ void cgroup_rstat_updated(struct cgroup *cgrp, int cpu) struct cgroup *parent; unsigned long flags; + /* nothing to do for root */ + if (!cgroup_parent(cgrp)) + return; + /* * Paired with the one in cgroup_rstat_cpu_pop_upated(). Either we * see NULL updated_next or they see our updated stat. -- 2.9.5
