linux-kernel - [PATCH v4 10/40] dmaengine: idxd: optimize perfmon_assign

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Date: Thu, 20 Jun 2024 10:56:33 -0700
From: Yury Norov <yury.norov@...il.com>
To: linux-kernel@...r.kernel.org,
	Fenghua Yu <fenghua.yu@...el.com>,
	Dave Jiang <dave.jiang@...el.com>,
	Vinod Koul <vkoul@...nel.org>,
	dmaengine@...r.kernel.org
Cc: Yury Norov <yury.norov@...il.com>,
	Alexey Klimov <alexey.klimov@...aro.org>,
	Bart Van Assche <bvanassche@....org>,
	Jan Kara <jack@...e.cz>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Matthew Wilcox <willy@...radead.org>,
	Mirsad Todorovac <mirsad.todorovac@....unizg.hr>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Sergey Shtylyov <s.shtylyov@....ru>
Subject: [PATCH v4 10/40] dmaengine: idxd: optimize perfmon_assign_event()

The function searches used_mask for a set bit in a for-loop bit by
bit. Simplify it by using atomic find_and_set_bit(), and make a nice
one-liner.

Signed-off-by: Yury Norov <yury.norov@...il.com>
Reviewed-by: Dave Jiang <dave.jiang@...el.com>
Acked-by: Vinod Koul <vkoul@...nel.org>
Reviewed-by: Fenghua Yu <fenghua.yu@...el.com>
---
 drivers/dma/idxd/perfmon.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/drivers/dma/idxd/perfmon.c b/drivers/dma/idxd/perfmon.c
index 5e94247e1ea7..063ee78fb132 100644
--- a/drivers/dma/idxd/perfmon.c
+++ b/drivers/dma/idxd/perfmon.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 /* Copyright(c) 2020 Intel Corporation. All rights rsvd. */
 
+#include <linux/find_atomic.h>
 #include <linux/sched/task.h>
 #include <linux/io-64-nonatomic-lo-hi.h>
 #include "idxd.h"
@@ -134,13 +135,9 @@ static void perfmon_assign_hw_event(struct idxd_pmu *idxd_pmu,
 static int perfmon_assign_event(struct idxd_pmu *idxd_pmu,
 				struct perf_event *event)
 {
-	int i;
-
-	for (i = 0; i < IDXD_PMU_EVENT_MAX; i++)
-		if (!test_and_set_bit(i, idxd_pmu->used_mask))
-			return i;
+	int i = find_and_set_bit(idxd_pmu->used_mask, IDXD_PMU_EVENT_MAX);
 
-	return -EINVAL;
+	return i < IDXD_PMU_EVENT_MAX ? i : -EINVAL;
 }
 
 /*
-- 
2.43.0