| From | Vitaly Kuznetsov <> | Subject | Re: [PATCH 43/54] drivers/hv: replace cpumask_weight with cpumask_weight_eq | Date | Mon, 24 Jan 2022 10:20:13 +0100 |
| |
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
|