On Thu, Jan 11, 2024 at 1:52 AM Alexei Starovoitov
<alexei.starovoitov@xxxxxxxxx> wrote:
>
> On Tue, Jan 9, 2024 at 10:00 PM Yafang Shao <laoar.shao@xxxxxxxxx> wrote:
> > +
> > +SEC("iter/cgroup")
> > +int BPF_PROG(cpu_cgroup, struct bpf_iter_meta *meta, struct cgroup *cgrp)
> > +{
> > + u32 *cpu, nr_running = 0, psi_nr_running = 0, nr_cpus = 0;
> > + unsigned int tasks[NR_PSI_TASK_COUNTS];
> > + struct psi_group_cpu *groupc;
> > + struct bpf_cpumask *mask;
> > + struct task_struct *p;
> > + struct rq *rq;
> > +
> > + /* epilogue */
> > + if (cgrp == NULL)
> > + return 0;
> > +
> > + mask = bpf_cpumask_create();
> > + if (!mask)
> > + return 1;
> > +
> > + p = bpf_task_from_pid(target_pid);
> > + if (!p) {
> > + bpf_cpumask_release(mask);
> > + return 1;
> > + }
> > +
> > + bpf_cpumask_copy(mask, p->cpus_ptr);
> > + bpf_for_each(cpumask, cpu, &mask->cpumask) {
> > + rq = (struct rq *)bpf_per_cpu_ptr(&runqueues, *cpu);
> > + if (!rq)
> > + continue;
> > + nr_running += rq->nr_running;
> > + nr_cpus += 1;
> > +
> > + groupc = (struct psi_group_cpu *)bpf_per_cpu_ptr(&system_group_pcpu, *cpu);
> > + if (!groupc)
> > + continue;
> > + bpf_probe_read_kernel(&tasks, sizeof(tasks), &groupc->tasks);
> > + psi_nr_running += tasks[NR_RUNNING];
> > + }
>
> Instead of probe_read_kernel (which is not fast) please use
> bpf_rdonly_cast() and access groups->tasks.
> array should already be recognized by the verifier, but if not let's
> fix the verifier instead of fallback to probe_read.
Thanks for your suggestion.
Will do it.
--
Regards
Yafang
