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Message-Id: <20231101225820.51342-5-yury.norov@gmail.com>
Date: Wed, 1 Nov 2023 15:58:20 -0700
From: Yury Norov <yury.norov@...il.com>
To: Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org
Cc: Yury Norov <yury.norov@...il.com>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
Rasmus Villemoes <linux@...musvillemoes.dk>
Subject: [PATCH 4/4] lib/group_cpus: optimize outer loop in grp_spread_init_one()
Similarly to the inner loop, in the outer loop we can use for_each_cpu()
macro, and skip cpus that have been copied.
With this patch, the function becomes O(1), despite that it's a
double-loop.
Signed-off-by: Yury Norov <yury.norov@...il.com>
---
lib/group_cpus.c | 12 ++++--------
1 file changed, 4 insertions(+), 8 deletions(-)
diff --git a/lib/group_cpus.c b/lib/group_cpus.c
index 8afe0c71d204..2442b38cbf37 100644
--- a/lib/group_cpus.c
+++ b/lib/group_cpus.c
@@ -17,16 +17,11 @@ static void grp_spread_init_one(struct cpumask *irqmsk, struct cpumask *nmsk,
const struct cpumask *siblmsk;
int cpu, sibl;
- for ( ; cpus_per_grp > 0; ) {
- cpu = cpumask_first(nmsk);
-
- /* Should not happen, but I'm too lazy to think about it */
- if (cpu >= nr_cpu_ids)
- return;
-
+ for_each_cpu(cpu, nmsk) {
__cpumask_clear_cpu(cpu, nmsk);
__cpumask_set_cpu(cpu, irqmsk);
- cpus_per_grp--;
+ if (cpus_per_grp-- == 0)
+ return;
/* If the cpu has siblings, use them first */
siblmsk = topology_sibling_cpumask(cpu);
@@ -37,6 +32,7 @@ static void grp_spread_init_one(struct cpumask *irqmsk, struct cpumask *nmsk,
__cpumask_set_cpu(sibl, irqmsk);
if (cpus_per_grp-- == 0)
return;
+ cpu = sibl + 1;
}
}
}
--
2.39.2
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