linux-kernel - Re: [PATCH 2/9] lib/bitmap: implement bitmap_{empty,full} with bitmap_weight

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Message-ID: <YaMHfzZ5PBn0714Z@qmqm.qmqm.pl>
Date:   Sun, 28 Nov 2021 05:37:19 +0100
From:   Michał Mirosław <mirq-linux@...e.qmqm.pl>
To:     Yury Norov <yury.norov@...il.com>
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Subject: Re: [PATCH 2/9] lib/bitmap: implement bitmap_{empty,full} with
 bitmap_weight_eq()

On Sat, Nov 27, 2021 at 07:56:57PM -0800, Yury Norov wrote:
> Now as we have bitmap_weight_eq(), switch bitmap_full() and
> bitmap_empty() to using it.
[...]
> -static inline bool bitmap_empty(const unsigned long *src, unsigned nbits)
> -{
> -	if (small_const_nbits(nbits))
> -		return ! (*src & BITMAP_LAST_WORD_MASK(nbits));
> -
> -	return find_first_bit(src, nbits) == nbits;
> -}
[...]
> +static __always_inline bool bitmap_empty(const unsigned long *src, unsigned int nbits)
> +{
> +	return bitmap_weight_eq(src, nbits, 0);
> +}
[..]

What's the speed difference? Have you benchmarked this?

Best Regards
Michał Mirosław