Re: [PATCH v2 3/8] sched/topology: add for_each_numa_cpu() macro

Yury Norov
2023-04-26T05:32:43Z

On Tue, Apr 25, 2023 at 10:54:48AM +0100, Valentin Schneider wrote:
> On 19/04/23 22:19, Yury Norov wrote:
> > +/**
> > + * for_each_numa_cpu - iterate over cpus in increasing order taking into account
> > + * NUMA distances from a given node.
> > + * @cpu: the (optionally unsigned) integer iterator
> > + * @hop: the iterator variable, must be initialized to a desired minimal hop.
> > + * @node: the NUMA node to start the search from.
> > + * @mask: the cpumask pointer
> > + *
> > + * Requires rcu_lock to be held.
> > + */
> > +#define for_each_numa_cpu(cpu, hop, node, mask) \
> > + for ((cpu) = 0, (hop) = 0; \
> > + (cpu) = sched_numa_find_next_cpu((mask), (cpu), (node), &(hop)),\
> > + (cpu) < nr_cpu_ids; \
> > + (cpu)++)
> > +
>
> I think we can keep sched_numa_find_next_cpu() as-is, but could we make
> that macro use cpu_possible_mask by default? We can always add a variant
> if/when we need to feed in a different mask.

As mentioned in discussion to the driver's patch, all that numa things
imply only online CPUs, so cpu_possible_mask may mislead to some extent.

Anyways, can you elaborate what you exactly want? Like this?

#define for_each_numa_online_cpu(cpu, hop, node) \
for_each_numa_cpu(cpu, hop, node, cpu_online_mask)