On Fri, Nov 11, 2022 at 09:07:17AM -0800, Yury Norov wrote:
> On Fri, Nov 11, 2022 at 01:42:29PM +0200, Andy Shevchenko wrote:
> > On Thu, Nov 10, 2022 at 08:00:26PM -0800, Yury Norov wrote:
> > > + int w, ret = nr_cpu_ids;
> > > +
> > > + rcu_read_lock();
> > > + masks = rcu_dereference(sched_domains_numa_masks);
> > > + if (!masks)
> > > + goto out;
> > > +
> > > + while (last >= first) {
> > > + mid = (last + first) / 2;
> > > +
> > > + if (cpumask_weight_and(cpus, masks[mid][node]) <= cpu) {
> > > + first = mid + 1;
> > > + continue;
> > > + }
> > > +
> > > + w = (mid == 0) ? 0 : cpumask_weight_and(cpus, masks[mid - 1][node]);
> >
> > See below.
> >
> > > + if (w <= cpu)
> > > + break;
> > > +
> > > + last = mid - 1;
> > > + }
> >
> > We have lib/bsearch.h. I haven't really looked deeply into the above, but my
> > gut feelings that that might be useful here. Can you check that?
>
> Yes we do. I tried it, and it didn't work because nodes arrays are
> allocated dynamically, and distance between different pairs of hops
> for a given node is not a constant, which is a requirement for
> bsearch.
>
> However, distance between hops pointers in 1st level array should be
> constant, and we can try feeding bsearch with it. I'll experiment with
> bsearch for more.
OK, I tried bsearch on array of hops, and it works. But it requires
adding some black pointers magic. I'll send v2 based on bsearch soon.
Thanks,
Yury
