Re: [PATCH 12/49] perf: replace bitmap_weight with bitmap_empty where appropriate

Christophe JAILLET
2022-02-11T17:29:33Z

Le 10/02/2022 à 23:48, Yury Norov a écrit :
> In some places, drivers/perf code calls bitmap_weight() to check if any
> bit of a given bitmap is set. It's better to use bitmap_empty() in that
> case because bitmap_empty() stops traversing the bitmap as soon as it
> finds first set bit, while bitmap_weight() counts all bits unconditionally.
>
> Signed-off-by: Yury Norov <yury.norov@gmail.com>
> ---
> drivers/perf/arm-cci.c | 2 +-
> drivers/perf/arm_pmu.c | 4 ++--
> drivers/perf/hisilicon/hisi_uncore_pmu.c | 2 +-
> drivers/perf/xgene_pmu.c | 2 +-
> 4 files changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/perf/arm-cci.c b/drivers/perf/arm-cci.c
> index 54aca3a62814..96e09fa40909 100644
> --- a/drivers/perf/arm-cci.c
> +++ b/drivers/perf/arm-cci.c
> @@ -1096,7 +1096,7 @@ static void cci_pmu_enable(struct pmu *pmu)
> {
> struct cci_pmu *cci_pmu = to_cci_pmu(pmu);
> struct cci_pmu_hw_events *hw_events = &cci_pmu->hw_events;
> - int enabled = bitmap_weight(hw_events->used_mask, cci_pmu->num_cntrs);
> + bool enabled = !bitmap_empty(hw_events->used_mask, cci_pmu->num_cntrs);
> unsigned long flags;
>
> if (!enabled)
> diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c
> index 295cc7952d0e..a31b302b0ade 100644
> --- a/drivers/perf/arm_pmu.c
> +++ b/drivers/perf/arm_pmu.c
> @@ -524,7 +524,7 @@ static void armpmu_enable(struct pmu *pmu)
> {
> struct arm_pmu *armpmu = to_arm_pmu(pmu);
> struct pmu_hw_events *hw_events = this_cpu_ptr(armpmu->hw_events);
> - int enabled = bitmap_weight(hw_events->used_mask, armpmu->num_events);
> + bool enabled = !bitmap_empty(hw_events->used_mask, armpmu->num_events);
>
> /* For task-bound events we may be called on other CPUs */
> if (!cpumask_test_cpu(smp_processor_id(), &armpmu->supported_cpus))
> @@ -785,7 +785,7 @@ static int cpu_pm_pmu_notify(struct notifier_block *b, unsigned long cmd,
> {
> struct arm_pmu *armpmu = container_of(b, struct arm_pmu, cpu_pm_nb);
> struct pmu_hw_events *hw_events = this_cpu_ptr(armpmu->hw_events);
> - int enabled = bitmap_weight(hw_events->used_mask, armpmu->num_events);
> + bool enabled = !bitmap_empty(hw_events->used_mask, armpmu->num_events);
>
> if (!cpumask_test_cpu(smp_processor_id(), &armpmu->supported_cpus))
> return NOTIFY_DONE;
> diff --git a/drivers/perf/hisilicon/hisi_uncore_pmu.c b/drivers/perf/hisilicon/hisi_uncore_pmu.c
> index a738aeab5c04..358e4e284a62 100644
> --- a/drivers/perf/hisilicon/hisi_uncore_pmu.c
> +++ b/drivers/perf/hisilicon/hisi_uncore_pmu.c
> @@ -393,7 +393,7 @@ EXPORT_SYMBOL_GPL(hisi_uncore_pmu_read);
> void hisi_uncore_pmu_enable(struct pmu *pmu)
> {
> struct hisi_pmu *hisi_pmu = to_hisi_pmu(pmu);
> - int enabled = bitmap_weight(hisi_pmu->pmu_events.used_mask,
> + bool enabled = !bitmap_empty(hisi_pmu->pmu_events.used_mask,
> hisi_pmu->num_counters);
>
> if (!enabled)
> diff --git a/drivers/perf/xgene_pmu.c b/drivers/perf/xgene_pmu.c
> index 5283608dc055..0c32dffc7ede 100644
> --- a/drivers/perf/xgene_pmu.c
> +++ b/drivers/perf/xgene_pmu.c
> @@ -867,7 +867,7 @@ static void xgene_perf_pmu_enable(struct pmu *pmu)
> {
> struct xgene_pmu_dev *pmu_dev = to_pmu_dev(pmu);
> struct xgene_pmu *xgene_pmu = pmu_dev->parent;
> - int enabled = bitmap_weight(pmu_dev->cntr_assign_mask,
> + bool enabled = !bitmap_empty(pmu_dev->cntr_assign_mask,
> pmu_dev->max_counters);

Would it make sense to call it 'disabled', remove the "!"...

>
> if (!enabled)
... and 'if (disabled)' here?

Just my 2c,

CJ