Re: [PATCH 33/49] perf: replace bitmap_weight with bitmap_weight_eq for ThunderX2

Mark Rutland
2022-02-11T10:32:08Z

On Thu, Feb 10, 2022 at 02:49:17PM -0800, Yury Norov wrote:
> tx2_uncore_event_start() calls bitmap_weight() to compare the weight
> of bitmap with a given number. We can do it more efficiently with
> bitmap_weight_eq because conditional bitmap_weight may stop traversing
> the bitmap earlier, as soon as condition is (or can't be) met.
>
> Signed-off-by: Yury Norov <yury.norov@gmail.com>

Given the max counters value is either 4 or 8 I doubt this should matter, but
for consistenct this is fine, so:

Acked-by: Mark Rutland <mark.rutland@arm.com>

I now see bitmap_weight_eq() is introduced within this series, so I assume you
need to queue that and its users together, and will want to take the prior
drivers/perf/ bit together with that.

Thanks,
Mark.

> ---
> drivers/perf/thunderx2_pmu.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/perf/thunderx2_pmu.c b/drivers/perf/thunderx2_pmu.c
> index 1edb9c03704f..97d5b39778fa 100644
> --- a/drivers/perf/thunderx2_pmu.c
> +++ b/drivers/perf/thunderx2_pmu.c
> @@ -623,8 +623,8 @@ static void tx2_uncore_event_start(struct perf_event *event, int flags)
> return;
>
> /* Start timer for first event */
> - if (bitmap_weight(tx2_pmu->active_counters,
> - tx2_pmu->max_counters) == 1) {
> + if (bitmap_weight_eq(tx2_pmu->active_counters,
> + tx2_pmu->max_counters, 1)) {
> hrtimer_start(&tx2_pmu->hrtimer,
> ns_to_ktime(tx2_pmu->hrtimer_interval),
> HRTIMER_MODE_REL_PINNED);
> --
> 2.32.0