linux-kernel - Re: [RFC PATCH v1 3/6] cpumask: Implement cpumask_{first,next}

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Message-ID: <c494e91f-abb1-4d09-acec-a6003bf8270b@efficios.com>
Date: Fri, 23 Aug 2024 16:49:02 -0400
From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To: Yury Norov <yury.norov@...il.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
 linux-kernel@...r.kernel.org, Valentin Schneider <vschneid@...hat.com>,
 Mel Gorman <mgorman@...e.de>, Steven Rostedt <rostedt@...dmis.org>,
 Vincent Guittot <vincent.guittot@...aro.org>,
 Dietmar Eggemann <dietmar.eggemann@....com>, Ben Segall
 <bsegall@...gle.com>, Rasmus Villemoes <linux@...musvillemoes.dk>,
 Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [RFC PATCH v1 3/6] cpumask: Implement
 cpumask_{first,next}_{nor,andnot}

On 2024-08-23 21:18, Yury Norov wrote:
> 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@...icios.com>
>> Cc: Yury Norov <yury.norov@...il.com>
>> Cc: Rasmus Villemoes <linux@...musvillemoes.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.

Will fix the 4 instances here for next round.

Thanks,

Mathieu

> 
>> +}
>> +
>> +/**
>> + * 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

-- 
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com