linux-kernel - [PATCH 04/14] powerpc/xmon: simplify xmon_batch_next

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Message-ID: <20241228184949.31582-5-yury.norov@gmail.com>
Date: Sat, 28 Dec 2024 10:49:36 -0800
From: Yury Norov <yury.norov@...il.com>
To: linux-kernel@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org,
	Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	Naveen N Rao <naveen@...nel.org>,
	Madhavan Srinivasan <maddy@...ux.ibm.com>
Cc: Yury Norov <yury.norov@...il.com>,
	Rasmus Villemoes <linux@...musvillemoes.dk>
Subject: [PATCH 04/14] powerpc/xmon: simplify xmon_batch_next_cpu()

The function opencodes for_each_cpu_wrap() macro. As a loop termination
condition it uses cpumask_empty(), which is O(N), and it makes the whole
algorithm O(N^2). Switching to for_each_cpu_wrap() simplifies the logic,
and makes the algorithm linear.

Signed-off-by: Yury Norov <yury.norov@...il.com>
---
 arch/powerpc/xmon/xmon.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index f4e841a36458..d7809f15dc68 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -1271,11 +1271,7 @@ static int xmon_batch_next_cpu(void)
 {
 	unsigned long cpu;
 
-	while (!cpumask_empty(&xmon_batch_cpus)) {
-		cpu = cpumask_next_wrap(smp_processor_id(), &xmon_batch_cpus,
-					xmon_batch_start_cpu, true);
-		if (cpu >= nr_cpu_ids)
-			break;
+	for_each_cpu_wrap(cpu, &xmon_batch_cpus, xmon_batch_start_cpu) {
 		if (xmon_batch_start_cpu == -1)
 			xmon_batch_start_cpu = cpu;
 		if (xmon_switch_cpu(cpu))
-- 
2.43.0