Messages in this thread | | | Date | Thu, 7 Dec 2023 14:07:25 -0800 | From | Yury Norov <> | Subject | Re: [PATCH v2 3/6] lib/group_cpus: optimize inner loop in grp_spread_init_one() |
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On Thu, Dec 07, 2023 at 01:45:21PM -0800, Andrew Morton wrote: > On Thu, 7 Dec 2023 12:38:57 -0800 Yury Norov <yury.norov@gmail.com> wrote: > > > The loop starts from the beginning every time we switch to the next > > sibling mask. This is the Schlemiel the Painter's style of coding > > because we know for sure that nmsk is clear up to current CPU, and we > > can just continue from the next CPU. > > > > Also, we can do it nicer if leverage the dedicated for_each() iterator. > > > > --- a/lib/group_cpus.c > > +++ b/lib/group_cpus.c > > @@ -30,13 +30,13 @@ static void grp_spread_init_one(struct cpumask *irqmsk, struct cpumask *nmsk, > > > > /* If the cpu has siblings, use them first */ > > siblmsk = topology_sibling_cpumask(cpu); > > - for (sibl = -1; cpus_per_grp > 0; ) { > > - sibl = cpumask_next(sibl, siblmsk); > > - if (sibl >= nr_cpu_ids) > > - break; > > I assume this test goes away because the iterator takes care of it?
Yes, correct.
> > > + sibl = cpu + 1; > > + > > + for_each_cpu_and_from(sibl, siblmsk, nmsk) { > > __cpumask_clear_cpu(sibl, nmsk); > > __cpumask_set_cpu(sibl, irqmsk); > > - cpus_per_grp--; > > + if (cpus_per_grp-- == 0) > > + return; > > } > > } > > }
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