Re: [PATCH 2/8] sched/topology: introduce sched_numa_find_next_cpu()

Yury Norov
2023-04-10T18:00:37Z

On Mon, Mar 27, 2023 at 01:28:12PM +0300, Andy Shevchenko wrote:
> On Sat, Mar 25, 2023 at 11:55:08AM -0700, Yury Norov wrote:
> > The function searches for the next CPU in a given cpumask according to
> > NUMA topology, so that it traverses cpus per-hop.
> >
> > If the CPU is the last cpu in a given hop, sched_numa_find_next_cpu()
> > switches to the next hop, and picks the first CPU from there, excluding
> > those already traversed.
>
> ...
>
> > +/*
>
> Hmm... Is it deliberately not a kernel doc?

Yes, I'd prefer to encourage people to use for_each() approach instead
of calling it directly.

If there will be a good reason to make it a more self-consistent thing,
we'll have to add a wrapper, just like sched_numa_find_nth_cpu() is
wrapped with cpumask_local_spread(). Particularly, use RCU lock/unlock
and properly handle NUMA_NO_NODE.

> > + * sched_numa_find_next_cpu() - given the NUMA topology, find the next cpu
> > + * cpumask: cpumask to find a cpu from
> > + * cpu: current cpu
> > + * node: local node
> > + * hop: (in/out) indicates distance order of current CPU to a local node
> > + *
> > + * The function searches for next cpu at a given NUMA distance, indicated
> > + * by hop, and if nothing found, tries to find CPUs at a greater distance,
> > + * starting from the beginning.
> > + *
> > + * returns: cpu, or >= nr_cpu_ids when nothing found.
> > + */
>
> --
> With Best Regards,
> Andy Shevchenko
>