mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-23 17:30:02 +00:00
cgroup, rstat: Don't flush subtree root unless necessary
cgroup_rstat_cpu_pop_updated() is used to traverse the updated cgroups on flush. While it was only visiting updated ones in the subtree, it was visiting @root unconditionally. We can easily check whether @root is updated or not by looking at its ->updated_next just as with the cgroups in the subtree. * Remove the unnecessary cgroup_parent() test. The system root cgroup is never updated and thus its ->updated_next is always NULL. No need to test whether cgroup_parent() exists in addition to ->updated_next. * Terminate traverse if ->updated_next is NULL. This can only happen for subtree @root and there's no reason to visit it if it's not marked updated. This reduces cpu consumption when reading a lot of rstat backed files. In a micro benchmark reading stat from ~1600 cgroups, the sys time was lowered by >40%. Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
parent
05b71f6ffd
commit
b4ff1b44bc
1 changed files with 6 additions and 4 deletions
|
@ -87,7 +87,6 @@ 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;
|
||||
|
@ -115,8 +114,8 @@ 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.
|
||||
*/
|
||||
parent = cgroup_parent(pos);
|
||||
if (parent && rstatc->updated_next) {
|
||||
if (rstatc->updated_next) {
|
||||
struct cgroup *parent = cgroup_parent(pos);
|
||||
struct cgroup_rstat_cpu *prstatc = cgroup_rstat_cpu(parent, cpu);
|
||||
struct cgroup_rstat_cpu *nrstatc;
|
||||
struct cgroup **nextp;
|
||||
|
@ -140,9 +139,12 @@ static struct cgroup *cgroup_rstat_cpu_pop_updated(struct cgroup *pos,
|
|||
* updated stat.
|
||||
*/
|
||||
smp_mb();
|
||||
|
||||
return pos;
|
||||
}
|
||||
|
||||
return pos;
|
||||
/* only happens for @root */
|
||||
return NULL;
|
||||
}
|
||||
|
||||
/* see cgroup_rstat_flush() */
|
||||
|
|
Loading…
Reference in a new issue