2023-11-18 15:53:51

by Yury Norov

Subject: [PATCH 09/34] dmaengine: idxd: optimize perfmon_assign_event()

The function searches used_mask for a set bit in a for-loop bit by bit.
We can do it faster by using atomic find_and_set_bit().

Signed-off-by: Yury Norov <[email protected]>
---
drivers/dma/idxd/perfmon.c | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/drivers/dma/idxd/perfmon.c b/drivers/dma/idxd/perfmon.c
index fdda6d604262..4dd9c0d979c3 100644
--- a/drivers/dma/idxd/perfmon.c
+++ b/drivers/dma/idxd/perfmon.c
@@ -134,13 +134,9 @@ 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;
}

/*
--
2.39.2

2023-11-20 15:36:31

by Dave Jiang

Subject: Re: [PATCH 09/34] dmaengine: idxd: optimize perfmon_assign_event()

On 11/18/23 08:50, Yury Norov wrote:
> The function searches used_mask for a set bit in a for-loop bit by bit.
> We can do it faster by using atomic find_and_set_bit().
>
> Signed-off-by: Yury Norov <[email protected]>

Reviewed-by: Dave Jiang <[email protected]>
> ---
> drivers/dma/idxd/perfmon.c | 8 ++------
> 1 file changed, 2 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/dma/idxd/perfmon.c b/drivers/dma/idxd/perfmon.c
> index fdda6d604262..4dd9c0d979c3 100644
> --- a/drivers/dma/idxd/perfmon.c
> +++ b/drivers/dma/idxd/perfmon.c
> @@ -134,13 +134,9 @@ 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;
> }
>
> /*

2023-11-24 12:17:36

by Vinod Koul

Subject: Re: [PATCH 09/34] dmaengine: idxd: optimize perfmon_assign_event()

On 18-11-23, 07:50, Yury Norov wrote:
> The function searches used_mask for a set bit in a for-loop bit by bit.
> We can do it faster by using atomic find_and_set_bit().

Acked-by: Vinod Koul <[email protected]>

--
~Vinod