Re: [PATCH v2 7/8] lib: add test for for_each_numa_{cpu,hop_mask}()

[Valentin Schneider <vschneid@xxxxxxxxxx>]

On 19/04/23 22:19, Yury Norov wrote:
> +	for (node = 0; node < sched_domains_numa_levels; node++) {
> +		unsigned int hop, c = 0;
> +
> +		rcu_read_lock();
> +		for_each_numa_cpu(cpu, hop, node, cpu_online_mask)
> +			expect_eq_uint(cpumask_local_spread(c++, node), cpu);
> +		rcu_read_unlock();
> +	}

I'm not fond of the export of sched_domains_numa_levels, especially
considering it's just there for tests.

Furthermore, is there any value is testing parity with
cpumask_local_spread()? Rather, shouldn't we check that using this API does
yield CPUs of increasing NUMA distance?

Something like

        for_each_node(node) {
                unsigned int prev_cpu, hop = 0;

                cpu = cpumask_first(cpumask_of_node(node));
                prev_cpu = cpu;

                rcu_read_lock();

                /* Assert distance is monotonically increasing */
                for_each_numa_cpu(cpu, hop, node, cpu_online_mask) {
                        expect_ge_uint(cpu_to_node(cpu), cpu_to_node(prev_cpu));
                        prev_cpu = cpu;
                }

                rcu_read_unlock();
        }