Messages in this thread Patch in this message | | | Date | Sat, 20 Jan 2024 11:17:00 +0800 | From | Ming Lei <> | Subject | Re: [PATCH 2/9] lib/group_cpus: optimize inner loop in grp_spread_init_one() |
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On Fri, Jan 19, 2024 at 06:50:46PM -0800, Yury Norov 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, > and simplify the logic of clearing a bit in nmsk. > > Signed-off-by: Yury Norov <yury.norov@gmail.com> > --- > lib/group_cpus.c | 14 +++++++------- > 1 file changed, 7 insertions(+), 7 deletions(-) > > diff --git a/lib/group_cpus.c b/lib/group_cpus.c > index ee272c4cefcc..063ed9ae1b8d 100644 > --- a/lib/group_cpus.c > +++ b/lib/group_cpus.c > @@ -30,14 +30,14 @@ 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; > - if (!cpumask_test_and_clear_cpu(sibl, nmsk)) > - continue; > + sibl = cpu + 1;
No, it is silly to let 'sibl' point to 'cpu + 1', cause we just want to iterate over 'siblmsk & nmsk', and nothing to do with the next cpu('cpu + 1').
> + > + for_each_cpu_and_from(sibl, siblmsk, nmsk) { > + if (cpus_per_grp-- == 0) > + return; > + > + cpumask_clear_cpu(sibl, nmsk); > cpumask_set_cpu(sibl, irqmsk); > - cpus_per_grp--;
Andrew, please replace the 1st two patches with the following one:
From 7a983ee5e1b4f05e5ae26c025dffd801b909e2f3 Mon Sep 17 00:00:00 2001 From: Ming Lei <ming.lei@redhat.com> Date: Sat, 20 Jan 2024 11:07:26 +0800 Subject: [PATCH] lib/group_cpus.c: simplify grp_spread_init_one()
What the inner loop needs to do is to iterate over `siblmsk & nmsk`, and clear the cpu in 'nmsk' and set it in 'irqmsk'.
Clean it by for_each_cpu_and().
This is based on Yury Norov's patch, which needs one extra for_each_cpu_and_from(), which is really not necessary.
Signed-off-by: Ming Lei <ming.lei@redhat.com> --- lib/group_cpus.c | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-)
diff --git a/lib/group_cpus.c b/lib/group_cpus.c index ee272c4cefcc..564d8e817f65 100644 --- a/lib/group_cpus.c +++ b/lib/group_cpus.c @@ -30,14 +30,11 @@ 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; - if (!cpumask_test_and_clear_cpu(sibl, nmsk)) - continue; + for_each_cpu_and(sibl, siblmsk, nmsk) { + cpumask_clear_cpu(sibl, nmsk); cpumask_set_cpu(sibl, irqmsk); - cpus_per_grp--; + if (--cpus_per_grp == 0) + return; } } } -- 2.42.0
Thanks, Ming
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