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

[Dave Jiang]

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 <yury.norov@xxxxxxxxx>

Reviewed-by: Dave Jiang <dave.jiang@xxxxxxxxx>
> ---
>  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;
>  }
>  
>  /*