Re: [patch V3 07/20] cpumask: Introduce cpumask_weighted_or()

Mathieu Desnoyers
2025-11-10T16:42:11Z

On 2025-11-10 11:11, Peter Zijlstra wrote:
> On Mon, Nov 03, 2025 at 02:29:59PM +0100, Thomas Gleixner wrote:
>> On Mon, Nov 03 2025 at 14:45, Shrikanth Hegde wrote:
>>> On 10/29/25 6:39 PM, Thomas Gleixner wrote:
>>>> +static __always_inline
>>>> +unsigned int cpumask_weighted_or(struct cpumask *dstp, const struct cpumask *src1p,
>>>> + const struct cpumask *src2p)
>>>> +{
>>>> + return bitmap_weighted_or(cpumask_bits(dstp), cpumask_bits(src1p),
>>>> + cpumask_bits(src2p), small_cpumask_bits);
>>>> +}
>>>
>>> nit:
>>>
>>> We have currently cpumask_weight_and & variants.
>>> Wouldn't it be better to name it cpumask_weight_or ?
>>
>> No. cpumask_weight_and() does weight(mask1 & mask2) but this does
>
> The comment was about naming, notable: s/_weighted_or/_weight_or/g to
> better match the existing _weight_and().

But if we go for "_weight_or" to match "_weight_and", we end up with
the following different semantics between "or" and "and":

cpumask_weight_and():
inputs: mask1, mask2
outputs: none

return weight(mask1 & mask2);

cpumask_weight_or():
inputs: mask1, mask2
outputs: mask3

mask3 = mask1 | mask2;
return weight(mask3);

What we are trying to do here is apply a bitwise operation on two
inputs, write the resulting mask into mask3, *and* calculate the weight
as well, which is different from just calculating the weight.

Naming things is hard. I agree that the distinction between "weight" and
"weighted" is subtle.

Perhaps something along the lines of cpumask_eval_weight_or()
which would state the two operations performed (evaluate and calculate
the weight) could work ?

Thanks,

Mathieu

--
Mathieu Desnoyers
EfficiOS Inc.