Re: [PATCH 2/3] ice: use bitmap_weighted_xor() in ice_find_free_recp_res_idx()

[Tony Nguyen <anthony.l.nguyen@intel.com>]

On 2/22/2026 9:59 AM, Yury Norov wrote:
> On Tue, Dec 23, 2025 at 07:08:46PM +0000, David Laight wrote:
>> On Tue, 23 Dec 2025 11:23:01 -0500
>> "Yury Norov (NVIDIA)" <yury.norov@gmail.com> wrote:
>>
>>> Use the right helper and save one bitmaps traverse.
>>
>> It makes no difference here.
> 
> No it makes.
> 
>> The bitmap has 48 entries and is just a single 'long' on 64bit.
>> It is also already in a very slow path that has iterated all the
>> 'set' bit of two bitmaps.
>>
>> The code is also pretty convoluted and confusing already.
>> One of the other bitmaps has 64 entries, recoding using u64 would
>> make it a bit more readable.
>>
>> Doing the 'weight' here is also just optimising for failure.
> 
> We've introduced bitmap_weighted_or() recently, and now we need to add
> siblings to the new sub-class. Regardless of performance impact in this
> case, having a dedicated helper for a typical operations saves a lot in
> debugging. This is proven by decades of code development.

I agree, performance issues aside, I could see the utility in having a 
combined helper. It makes is a little cleaner and removes a point for 
introducing problems. Assuming there are no objections, could you resend 
the series? It'll be easier than digging back to get these.

Thanks,
Tony

>> Oh, and using u8 and u16 for function parameters, return values and
>> maths requires extra instructions and is usually a bad idea.
> 
> Changing function signatures is not the patch purpose. Feel free to
> submit a separate patch.
> 
>> 	Dvaid
>>
>>>
>>> Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
>>> ---
>>>   drivers/net/ethernet/intel/ice/ice_switch.c | 4 +---
>>>   1 file changed, 1 insertion(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/net/ethernet/intel/ice/ice_switch.c b/drivers/net/ethernet/intel/ice/ice_switch.c
>>> index 84848f0123e7..903417477929 100644
>>> --- a/drivers/net/ethernet/intel/ice/ice_switch.c
>>> +++ b/drivers/net/ethernet/intel/ice/ice_switch.c
>>> @@ -4984,10 +4984,8 @@ ice_find_free_recp_res_idx(struct ice_hw *hw, const unsigned long *profiles,
>>>   			  hw->switch_info->recp_list[bit].res_idxs,
>>>   			  ICE_MAX_FV_WORDS);
>>>   
>>> -	bitmap_xor(free_idx, used_idx, possible_idx, ICE_MAX_FV_WORDS);
>>> -
>>>   	/* return number of free indexes */
>>> -	return (u16)bitmap_weight(free_idx, ICE_MAX_FV_WORDS);
>>> +	return (u16)bitmap_weighted_xor(free_idx, used_idx, possible_idx, ICE_MAX_FV_WORDS);
>>>   }
>>>   
>>>   /**