Re: [PATCH] sched/ext: add scx_bpf_cgroup_report_throttled kfunc

[Tejun Heo]

Hello,

On Mon, May 25, 2026 at 09:24:32PM +0200, Fernand Sieber wrote:
> +__bpf_kfunc void scx_bpf_cgroup_report_throttled(struct cgroup *cgrp,
> +						  u64 throttled_ns)
> +{
> +#ifdef CONFIG_CFS_BANDWIDTH
> +	struct task_group *tg;
> +
> +	rcu_read_lock();
> +	tg = cgrp->subsys[cpu_cgrp_id] ?
> +	     container_of(cgrp->subsys[cpu_cgrp_id], struct task_group, css) :
> +	     NULL;
> +	if (tg) {
> +		struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
> +
> +		raw_spin_lock_irq(&cfs_b->lock);
> +		cfs_b->throttled_time += throttled_ns;
> +		cfs_b->nr_throttled++;
> +		cfs_b->nr_periods++;
> +		raw_spin_unlock_irq(&cfs_b->lock);
> +	}
> +	rcu_read_unlock();
> +#endif

I don't think modifying fair's internal state from scx is a good idea. All
the cgroup piping is split at the interface level. I think it'd be better to
make both cfs and scx report their own numbers and then sum them up in the
output.

Thanks.

-- 
tejun