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From: Yury Norov <yury.norov@gmail.com>
To: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
	Michael Ellerman <mpe@ellerman.id.au>,
	Nicholas Piggin <npiggin@gmail.com>,
	Christophe Leroy <christophe.leroy@csgroup.eu>,
	Naveen N Rao <naveen@kernel.org>,
	Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Yury Norov <yury.norov@gmail.com>, Christoph Hellwig <hch@lst.de>,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>
Subject: [PATCH v2 04/13] powerpc/xmon: simplify xmon_batch_next_cpu()
Date: Tue, 28 Jan 2025 11:46:33 -0500	[thread overview]
Message-ID: <20250128164646.4009-5-yury.norov@gmail.com> (raw)
In-Reply-To: <20250128164646.4009-1-yury.norov@gmail.com>

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@gmail.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 268859e4df87..1acb53aab252 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



  parent reply	other threads:[~2025-01-28 16:47 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-01-28 16:46 [PATCH v2 00/13] cpumask: cleanup cpumask_next_wrap() implementation and usage Yury Norov
2025-01-28 16:46 ` [PATCH v2 03/13] ibmvnic: simplify ibmvnic_set_queue_affinity() Yury Norov
2025-02-05 23:10   ` Nick Child
2025-01-28 16:46 ` Yury Norov [this message]
2025-01-28 16:46 ` [PATCH v2 05/13] cpumask: deprecate cpumask_next_wrap() Yury Norov
2025-01-28 16:46 ` [PATCH v2 06/13] cpumask: re-introduce cpumask_next{,_and}_wrap() Yury Norov
2025-02-24 21:18 ` [PATCH v2 00/13] cpumask: cleanup cpumask_next_wrap() implementation and usage Michael S. Tsirkin

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