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SubjectRe: [PATCH v4 2/3] cgroup/rstat: Optimize cgroup_rstat_updated_list()
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On 11/28/23 11:43, Tejun Heo wrote:
> On Mon, Nov 27, 2023 at 11:01:22PM -0500, Waiman Long wrote:
> ...
>>> + * Recursively traverse down the cgroup_rstat_cpu updated tree and push
>>> + * parent first before its children into a singly linked list built from
>>> + * the tail backward like "pushing" cgroups into a stack. The parent is
>>> + * pushed by the caller. The recursion depth is the depth of the current
>>> + * updated subtree.
>>> + */
>>> +static struct cgroup *cgroup_rstat_push_children(struct cgroup *head,
>>> + struct cgroup_rstat_cpu *prstatc, int cpu)
>>> +{
>>> + struct cgroup *child, *parent;
>>> + struct cgroup_rstat_cpu *crstatc;
>>> +
>>> + parent = head;
>>> + child = prstatc->updated_children;
>>> + prstatc->updated_children = parent;
>>> +
>>> + /* updated_next is parent cgroup terminated */
>>> + while (child != parent) {
>>> + child->rstat_flush_next = head;
>>> + head = child;
>>> + crstatc = cgroup_rstat_cpu(child, cpu);
>>> + if (crstatc->updated_children != child)
>>> + head = cgroup_rstat_push_children(head, crstatc, cpu);
>>> + child = crstatc->updated_next;
>>> + crstatc->updated_next = NULL;
>>> + }
>>> + return head;
> The recursion bothers me. We don't really have a hard limit on nesting
> depth. We might need to add another pointer field but can make this
> iterative, right?

I see. Yes, I think it is possible to make it iterative. Using recursion
is just an easier way to do it. Will look into that.

Thanks,
Longman

>
> Thanks.
>

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