Re: [RFC PATCH v1 3/6] cpumask: Implement cpumask_{first,next}_{nor,andnot}

[Yury Norov <yury.norov@gmail.com>]

On Fri, Aug 23, 2024 at 02:59:43PM -0400, Mathieu Desnoyers wrote:
> Allow finding the first or next bit within two input cpumasks which is
> either:
> 
> - both zero and zero,
> - respectively one and zero.
> 
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> Cc: Yury Norov <yury.norov@gmail.com>
> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
> ---
> Changes since v0:
> - Rename "notandnot" to "nor".
> - Use __always_inline.
> ---
>  include/linux/cpumask.h | 60 +++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 60 insertions(+)
> 
> diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
> index 23686bed441d..5573e75c13ec 100644
> --- a/include/linux/cpumask.h
> +++ b/include/linux/cpumask.h
> @@ -204,6 +204,32 @@ unsigned int cpumask_first_and_and(const struct cpumask *srcp1,
>  				      cpumask_bits(srcp3), small_cpumask_bits);
>  }
>  
> +/**
> + * cpumask_first_andnot - return the first cpu from *srcp1 & ~*srcp2
> + * @src1p: the first input
> + * @src2p: the second input
> + *
> + * Returns >= nr_cpu_ids if no cpus match in both.
> + */
> +static __always_inline
> +unsigned int cpumask_first_andnot(const struct cpumask *srcp1, const struct cpumask *srcp2)
> +{
> +	return find_first_andnot_bit(cpumask_bits(srcp1), cpumask_bits(srcp2), nr_cpumask_bits);


Here should be a small_cpumask_bits. This is better optimized for
NR_CPUS < BITS_PER_LONG.

> +}
> +
> +/**
> + * cpumask_first_nor - return the first cpu from ~(*srcp1 | *srcp2)
> + * @src1p: the first input
> + * @src2p: the second input
> + *
> + * Returns >= nr_cpu_ids if no cpus match in both.
> + */
> +static __always_inline
> +unsigned int cpumask_first_nor(const struct cpumask *srcp1, const struct cpumask *srcp2)
> +{
> +	return find_first_nor_bit(cpumask_bits(srcp1), cpumask_bits(srcp2), nr_cpumask_bits);
> +}
> +
>  /**
>   * cpumask_last - get the last CPU in a cpumask
>   * @srcp:	- the cpumask pointer
> @@ -246,6 +272,40 @@ static inline unsigned int cpumask_next_zero(int n, const struct cpumask *srcp)
>  	return find_next_zero_bit(cpumask_bits(srcp), small_cpumask_bits, n+1);
>  }
>  
> +/**
> + * cpumask_next_andnot - return the next cpu from *srcp1 & ~*srcp2
> + * @n: the cpu prior to the place to search (ie. return will be > @n)
> + * @src1p: the first input
> + * @src2p: the second input
> + *
> + * Returns >= nr_cpu_ids if no cpus match in both.
> + */
> +static __always_inline
> +unsigned int cpumask_next_andnot(int n, const struct cpumask *srcp1, const struct cpumask *srcp2)
> +{
> +	/* -1 is a legal arg here. */
> +	if (n != -1)
> +		cpumask_check(n);
> +	return find_next_andnot_bit(cpumask_bits(srcp1), cpumask_bits(srcp2), nr_cpumask_bits, n+1);
> +}
> +
> +/**
> + * cpumask_next_nor - return the next cpu from ~(*srcp1 | *srcp2)
> + * @n: the cpu prior to the place to search (ie. return will be > @n)
> + * @src1p: the first input
> + * @src2p: the second input
> + *
> + * Returns >= nr_cpu_ids if no cpus match in both.
> + */
> +static __always_inline
> +unsigned int cpumask_next_nor(int n, const struct cpumask *srcp1, const struct cpumask *srcp2)
> +{
> +	/* -1 is a legal arg here. */
> +	if (n != -1)
> +		cpumask_check(n);
> +	return find_next_nor_bit(cpumask_bits(srcp1), cpumask_bits(srcp2), nr_cpumask_bits, n+1);
> +}
> +
>  #if NR_CPUS == 1
>  /* Uniprocessor: there is only one valid CPU */
>  static inline unsigned int cpumask_local_spread(unsigned int i, int node)
> -- 
> 2.39.2