linux-kernel - [PATCH] perf/arm-cci: Slightly optimize cci_pmu_sync

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Message-Id: <88d4e20d595f771396e9d558c1587eb4494057db.1682022422.git.christophe.jaillet@wanadoo.fr>
Date:   Thu, 20 Apr 2023 22:27:24 +0200
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     Will Deacon <will@...nel.org>, Mark Rutland <mark.rutland@....com>
Cc:     linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        linux-arm-kernel@...ts.infradead.org
Subject: [PATCH] perf/arm-cci: Slightly optimize cci_pmu_sync_counters()

When the 'mask' bitmap is cleared, it is better to use its full maximum
size instead of only the needed size.
This lets the compiler optimize it because the size is now known at compile
time. HW_CNTRS_MAX is small (i.e. currently 9), so a call to memset() is
saved.

Also, as 'mask' is local to the function, the non-atomic __set_bit() can
also safely be used here.

Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
---
 drivers/perf/arm-cci.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/perf/arm-cci.c b/drivers/perf/arm-cci.c
index 03b1309875ae..998259f1d973 100644
--- a/drivers/perf/arm-cci.c
+++ b/drivers/perf/arm-cci.c
@@ -645,7 +645,7 @@ static void cci_pmu_sync_counters(struct cci_pmu *cci_pmu)
 	struct cci_pmu_hw_events *cci_hw = &cci_pmu->hw_events;
 	DECLARE_BITMAP(mask, HW_CNTRS_MAX);
 
-	bitmap_zero(mask, cci_pmu->num_cntrs);
+	bitmap_zero(mask, HW_CNTRS_MAX);
 	for_each_set_bit(i, cci_pmu->hw_events.used_mask, cci_pmu->num_cntrs) {
 		struct perf_event *event = cci_hw->events[i];
 
@@ -656,7 +656,7 @@ static void cci_pmu_sync_counters(struct cci_pmu *cci_pmu)
 		if (event->hw.state & PERF_HES_STOPPED)
 			continue;
 		if (event->hw.state & PERF_HES_ARCH) {
-			set_bit(i, mask);
+			__set_bit(i, mask);
 			event->hw.state &= ~PERF_HES_ARCH;
 		}
 	}
-- 
2.34.1