[PATCH v4 09/40] drivers/perf: optimize ali_drw_get_counter_idx() by using find_and_set_bit()

Yury Norov
2024-06-20T17:57:35Z

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().

Signed-off-by: Yury Norov <yury.norov@gmail.com>
Acked-by: Will Deacon <will@kernel.org>
---
drivers/perf/alibaba_uncore_drw_pmu.c | 11 +++--------
1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/drivers/perf/alibaba_uncore_drw_pmu.c b/drivers/perf/alibaba_uncore_drw_pmu.c
index 38a2947ae813..1516f2c3d58f 100644
--- a/drivers/perf/alibaba_uncore_drw_pmu.c
+++ b/drivers/perf/alibaba_uncore_drw_pmu.c
@@ -17,6 +17,7 @@
#include <linux/cpumask.h>
#include <linux/device.h>
#include <linux/errno.h>
+#include <linux/find_atomic.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/kernel.h>
@@ -266,15 +267,9 @@ static const struct attribute_group *ali_drw_pmu_attr_groups[] = {
static int ali_drw_get_counter_idx(struct perf_event *event)
{
struct ali_drw_pmu *drw_pmu = to_ali_drw_pmu(event->pmu);
- int idx;
+ int idx = find_and_set_bit(drw_pmu->used_mask, ALI_DRW_PMU_COMMON_MAX_COUNTERS);

- for (idx = 0; idx < ALI_DRW_PMU_COMMON_MAX_COUNTERS; ++idx) {
- if (!test_and_set_bit(idx, drw_pmu->used_mask))
- return idx;
- }
-
- /* The counters are all in use. */
- return -EBUSY;
+ return idx < ALI_DRW_PMU_COMMON_MAX_COUNTERS ? idx : -EBUSY;
}

static u64 ali_drw_pmu_read_counter(struct perf_event *event)
--
2.43.0