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Date: Mon, 18 Dec 2023 13:19:06 -0800
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Subject: Re: [PATCH 1/3] cpumask: add cpumask_weight_andnot()
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To: Yury Norov <yury.norov@gmail.com>, Souradeep Chakrabarti
	<schakrabarti@linux.microsoft.com>, <kys@microsoft.com>,
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CC: <schakrabarti@microsoft.com>, <paulros@microsoft.com>
References: <20231217213214.1905481-1-yury.norov@gmail.com>
 <20231217213214.1905481-2-yury.norov@gmail.com>
From: Jacob Keller <jacob.e.keller@intel.com>
In-Reply-To: <20231217213214.1905481-2-yury.norov@gmail.com>
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On 12/17/2023 1:32 PM, Yury Norov wrote:
> Similarly to cpumask_weight_and(), cpumask_weight_andnot() is a handy
> helper that may help to avoid creating an intermediate mask just to
> calculate number of bits that set in a 1st given mask, and clear in 2nd
> one.
> 
> Signed-off-by: Yury Norov <yury.norov@gmail.com>

This seems reasonable to me.

Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>

> ---
>  include/linux/bitmap.h  | 12 ++++++++++++
>  include/linux/cpumask.h | 13 +++++++++++++
>  lib/bitmap.c            |  7 +++++++
>  3 files changed, 32 insertions(+)
> 
> diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
> index 99451431e4d6..5814e9ee40ba 100644
> --- a/include/linux/bitmap.h
> +++ b/include/linux/bitmap.h
> @@ -54,6 +54,7 @@ struct device;
>   *  bitmap_full(src, nbits)                     Are all bits set in *src?
>   *  bitmap_weight(src, nbits)                   Hamming Weight: number set bits
>   *  bitmap_weight_and(src1, src2, nbits)        Hamming Weight of and'ed bitmap
> + *  bitmap_weight_andnot(src1, src2, nbits)     Hamming Weight of andnot'ed bitmap
>   *  bitmap_set(dst, pos, nbits)                 Set specified bit area
>   *  bitmap_clear(dst, pos, nbits)               Clear specified bit area
>   *  bitmap_find_next_zero_area(buf, len, pos, n, mask)  Find bit free area
> @@ -169,6 +170,8 @@ bool __bitmap_subset(const unsigned long *bitmap1,
>  unsigned int __bitmap_weight(const unsigned long *bitmap, unsigned int nbits);
>  unsigned int __bitmap_weight_and(const unsigned long *bitmap1,
>  				 const unsigned long *bitmap2, unsigned int nbits);
> +unsigned int __bitmap_weight_andnot(const unsigned long *bitmap1,
> +				    const unsigned long *bitmap2, unsigned int nbits);
>  void __bitmap_set(unsigned long *map, unsigned int start, int len);
>  void __bitmap_clear(unsigned long *map, unsigned int start, int len);
>  
> @@ -425,6 +428,15 @@ unsigned long bitmap_weight_and(const unsigned long *src1,
>  	return __bitmap_weight_and(src1, src2, nbits);
>  }
>  
> +static __always_inline
> +unsigned long bitmap_weight_andnot(const unsigned long *src1,
> +				   const unsigned long *src2, unsigned int nbits)
> +{
> +	if (small_const_nbits(nbits))
> +		return hweight_long(*src1 & ~(*src2) & BITMAP_LAST_WORD_MASK(nbits));
> +	return __bitmap_weight_andnot(src1, src2, nbits);
> +}
> +
>  static __always_inline void bitmap_set(unsigned long *map, unsigned int start,
>  		unsigned int nbits)
>  {
> diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
> index cfb545841a2c..228c23eb36d2 100644
> --- a/include/linux/cpumask.h
> +++ b/include/linux/cpumask.h
> @@ -719,6 +719,19 @@ static inline unsigned int cpumask_weight_and(const struct cpumask *srcp1,
>  	return bitmap_weight_and(cpumask_bits(srcp1), cpumask_bits(srcp2), small_cpumask_bits);
>  }
>  
> +/**
> + * cpumask_weight_andnot - Count of bits in (*srcp1 & ~*srcp2)
> + * @srcp1: the cpumask to count bits (< nr_cpu_ids) in.
> + * @srcp2: the cpumask to count bits (< nr_cpu_ids) in.
> + *
> + * Return: count of bits set in both *srcp1 and *srcp2
> + */
> +static inline unsigned int cpumask_weight_andnot(const struct cpumask *srcp1,
> +						const struct cpumask *srcp2)
> +{
> +	return bitmap_weight_andnot(cpumask_bits(srcp1), cpumask_bits(srcp2), small_cpumask_bits);
> +}
> +
>  /**
>   * cpumask_shift_right - *dstp = *srcp >> n
>   * @dstp: the cpumask result
> diff --git a/lib/bitmap.c b/lib/bitmap.c
> index 09522af227f1..b97692854966 100644
> --- a/lib/bitmap.c
> +++ b/lib/bitmap.c
> @@ -348,6 +348,13 @@ unsigned int __bitmap_weight_and(const unsigned long *bitmap1,
>  }
>  EXPORT_SYMBOL(__bitmap_weight_and);
>  
> +unsigned int __bitmap_weight_andnot(const unsigned long *bitmap1,
> +				const unsigned long *bitmap2, unsigned int bits)
> +{
> +	return BITMAP_WEIGHT(bitmap1[idx] & ~bitmap2[idx], bits);
> +}
> +EXPORT_SYMBOL(__bitmap_weight_andnot);
> +
>  void __bitmap_set(unsigned long *map, unsigned int start, int len)
>  {
>  	unsigned long *p = map + BIT_WORD(start);