diff mbox series

[4/4] lib/group_cpus: optimize outer loop in grp_spread_init_one()

Message ID 20231101225820.51342-5-yury.norov@gmail.com
State New
Headers
Series lib/group_cpus: rework grp_spread_init_one() and make it O(1) |

Commit Message

Yury Norov Nov. 1, 2023, 10:58 p.m. UTC 
  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@gmail.com>
---
 lib/group_cpus.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)
diff mbox series

Patch

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;
 		}
 	}
 }