Re: [PATCH 2/2] cgroup/cpuset: Optimize cpuset_attach() on v2

[Michal Koutný]

On Sat, Nov 12, 2022 at 05:19:39PM -0500, Waiman Long <longman@xxxxxxxxxx> wrote:
> +	/*
> +	 * In the default hierarchy, enabling cpuset in the child cgroups
> +	 * will trigger a number of cpuset_attach() calls with no change
> +	 * in effective cpus and mems. In that case, we can optimize out
> +	 * by skipping the task iteration and update.
> +	 */
> +	if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&
> +	    !cpus_updated && !mems_updated) {

I'm just wondering -- why is this limited to the default hierarchy only?
IOW why can't v1 skip too (when favorable constness between cpusets).

Thanks,
Michal

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