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SubjectRe: [PATCH 43/54] drivers/hv: replace cpumask_weight with cpumask_weight_eq
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Yury Norov <yury.norov@gmail.com> writes:

> init_vp_index() calls cpumask_weight() to compare the weights of cpumasks
> We can do it more efficiently with cpumask_weight_eq because conditional
> cpumask_weight may stop traversing the cpumask earlier (at least one), as
> soon as condition is met.

Same comment as for "PATCH 41/54": cpumask_weight_eq() can only stop
earlier if the condition is not met, to prove the equality all bits need
always have to be examined.

>
> Signed-off-by: Yury Norov <yury.norov@gmail.com>
> ---
> drivers/hv/channel_mgmt.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
> index 60375879612f..7420a5fd47b5 100644
> --- a/drivers/hv/channel_mgmt.c
> +++ b/drivers/hv/channel_mgmt.c
> @@ -762,8 +762,8 @@ static void init_vp_index(struct vmbus_channel *channel)
> }
> alloced_mask = &hv_context.hv_numa_map[numa_node];
>
> - if (cpumask_weight(alloced_mask) ==
> - cpumask_weight(cpumask_of_node(numa_node))) {
> + if (cpumask_weight_eq(alloced_mask,
> + cpumask_weight(cpumask_of_node(numa_node)))) {

This code is not performace critical and I prefer the old version:

cpumask_weight() == cpumask_weight()

looks better than

cpumask_weight_eq(..., cpumask_weight())

(let alone the inner cpumask_of_node()) to me.

> /*
> * We have cycled through all the CPUs in the node;
> * reset the alloced map.

--
Vitaly

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