Re: [RFC PATCH 2/5] sched/events: Introduce cfs_rq load tracking trace event

[Dietmar Eggemann]

On 03/28/2017 09:56 AM, Peter Zijlstra wrote:
> On Tue, Mar 28, 2017 at 07:35:38AM +0100, Dietmar Eggemann wrote:

[...]

> >  (1) a root task_group:
> >
> >      cpu=4 path=/ id=1 load=6 util=331
>
> What's @id and why do we care?

It's a per cgroup/subsystem unique id for every task_group (cpu controller):

struct task_group {
	struct cgroup_subsys_state css {
		...
		int id;
                ...
	}
	...
}

The root task group path=/ has id=1 and all autogroups have id=0.

I agree, this id is redundant in case we have the task_group path.