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

[Yury Norov <ynorov@nvidia.com>]

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.

> 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);
> >  }
> >  
> >  /**