Hello. On Tue, Feb 09, 2021 at 11:33:00AM -0500, Johannes Weiner <han...@cmpxchg.org> wrote: > @@ -1971,10 +1978,14 @@ int cgroup_setup_root(struct cgroup_root *root, u16 > ss_mask) > if (ret) > goto destroy_root; > > - ret = rebind_subsystems(root, ss_mask); > + ret = cgroup_rstat_init(root_cgrp); Would it make sense to do cgroup_rstat_init() only if there's a subsys in ss_mask that makes use of rstat? (On legacy systems there could be individual hierarchy for each controller so the rstat space can be saved.)
> @@ -5159,11 +5170,9 @@ static struct cgroup *cgroup_create(struct cgroup
> *parent, const char *name,
> if (ret)
> goto out_free_cgrp;
>
> - if (cgroup_on_dfl(parent)) {
> - ret = cgroup_rstat_init(cgrp);
> - if (ret)
> - goto out_cancel_ref;
> - }
> + ret = cgroup_rstat_init(cgrp);
And here do cgroup_rstat_init() only when parent has it.
> @@ -285,8 +285,6 @@ void __init cgroup_rstat_boot(void)
>
> for_each_possible_cpu(cpu)
> raw_spin_lock_init(per_cpu_ptr(&cgroup_rstat_cpu_lock, cpu));
> -
> - BUG_ON(cgroup_rstat_init(&cgrp_dfl_root.cgrp));
> }
Regardless of the suggestion above, this removal obsoletes the comment
cgroup_rstat_init:
int cpu;
- /* the root cgrp has rstat_cpu preallocated */
if (!cgrp->rstat_cpu) {
cgrp->rstat_cpu = alloc_percpu(struct cgroup_rstat_cpu);
Regards,
Michal
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