[PATCH 2/2] cgroup/rstat: check updated_next only for root
From: Wei Yang <hidden>
Date: 2021-12-25 00:09:56
Also in:
lkml
Subsystem:
control group (cgroup), the rest · Maintainers:
Tejun Heo, Johannes Weiner, Michal Koutný, Linus Torvalds
After commit dc26532aed0a ("cgroup: rstat: punt root-level optimization to
individual controllers"), each rstat on updated_children list has its
->updated_next not NULL.
This means we can remove the check on ->updated_next, if we make sure
the subtree from @root is on list, which could be done by checking
updated_next for root.
Signed-off-by: Wei Yang <redacted>
---
kernel/cgroup/rstat.c | 46 +++++++++++++++++++++----------------------
1 file changed, 22 insertions(+), 24 deletions(-)
diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c
index a9d344e0521d..a00875375f7d 100644
--- a/kernel/cgroup/rstat.c
+++ b/kernel/cgroup/rstat.c@@ -88,6 +88,7 @@ static struct cgroup *cgroup_rstat_cpu_pop_updated(struct cgroup *pos, struct cgroup *root, int cpu) { struct cgroup_rstat_cpu *rstatc; + struct cgroup *parent; if (pos == root) return NULL;
@@ -96,9 +97,12 @@ static struct cgroup *cgroup_rstat_cpu_pop_updated(struct cgroup *pos, * We're gonna walk down to the first leaf and visit/remove it. We * can pick whatever unvisited node as the starting point. */ - if (!pos) + if (!pos) { pos = root; - else + // return NULL if this subtree is not on-list + if (!cgroup_rstat_cpu(pos, cpu)->updated_next) + return NULL; + } else pos = cgroup_parent(pos); /* walk down to the first leaf */
@@ -115,31 +119,25 @@ static struct cgroup *cgroup_rstat_cpu_pop_updated(struct cgroup *pos, * However, due to the way we traverse, @pos will be the first * child in most cases. The only exception is @root. */ - if (rstatc->updated_next) { - struct cgroup *parent = cgroup_parent(pos); - - if (parent) { - struct cgroup_rstat_cpu *prstatc; - struct cgroup **nextp; - - prstatc = cgroup_rstat_cpu(parent, cpu); - nextp = &prstatc->updated_children; - while (*nextp != pos) { - struct cgroup_rstat_cpu *nrstatc; - - nrstatc = cgroup_rstat_cpu(*nextp, cpu); - WARN_ON_ONCE(*nextp == parent); - nextp = &nrstatc->updated_next; - } - *nextp = rstatc->updated_next; - } + parent = cgroup_parent(pos); + if (parent) { + struct cgroup_rstat_cpu *prstatc; + struct cgroup **nextp; - rstatc->updated_next = NULL; - return pos; + prstatc = cgroup_rstat_cpu(parent, cpu); + nextp = &prstatc->updated_children; + while (*nextp != pos) { + struct cgroup_rstat_cpu *nrstatc; + + nrstatc = cgroup_rstat_cpu(*nextp, cpu); + WARN_ON_ONCE(*nextp == parent); + nextp = &nrstatc->updated_next; + } + *nextp = rstatc->updated_next; } - /* only happens for @root */ - return NULL; + rstatc->updated_next = NULL; + return pos; } /* see cgroup_rstat_flush() */
--
2.33.1