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cgroup/rstat: check updated_next only for root

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After commit dc26532aed ("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.

tj: Coding style fixes.

Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Wei Yang 2021-12-25 00:09:32 +00:00 committed by Tejun Heo
parent 0da41f7348
commit f5f60d235e
1 changed files with 21 additions and 22 deletions
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43
kernel/cgroup/rstat.c
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@ -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;
@ -96,10 +97,14 @@ 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 */
while (true) {
@ -115,31 +120,25 @@ 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);
parent = cgroup_parent(pos);
if (parent) {
struct cgroup_rstat_cpu *prstatc;
struct cgroup **nextp;
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;
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;
nrstatc = cgroup_rstat_cpu(*nextp, cpu);
WARN_ON_ONCE(*nextp == parent);
nextp = &nrstatc->updated_next;
}
rstatc->updated_next = NULL;
return pos;
*nextp = rstatc->updated_next;
}
/* only happens for @root */
return NULL;
rstatc->updated_next = NULL;
return pos;
}
/* see cgroup_rstat_flush() */