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Message-ID: <2c54b801-5f78-4f5a-bed0-a944ac5248e4@efficios.com>
Date: Fri, 23 Aug 2024 16:51:26 -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 2/6] lib: Implement find_{first,next,nth}_nor_bit,
find_first_andnot_bit
On 2024-08-23 21:19, Yury Norov wrote:
> On Fri, Aug 23, 2024 at 02:59:42PM -0400, Mathieu Desnoyers wrote:
>> Allow finding the first, next, or nth bit within two input bitmasks
>> which is zero in both masks.
>>
>> Allow fiding the first bit within two input bitmasks which is set in
>> first mask and cleared in the second mask. find_next_andnot_bit and
>> find_nth_andnot_bit already exist, so find the first bit appears to be
>> missing.
>>
>> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
>> Cc: Yury Norov <yury.norov@...il.com>
>> Cc: Rasmus Villemoes <linux@...musvillemoes.dk>
>
> Acked-by: Yury Norov <yury.norov@...il.com>
>
> If it comes to v2, can you also add some sanity tests for the new API?
I'm making a note to add those sanity tests before sending a v2.
Thanks,
Mathieu
>
>> ---
>> Changes since v0:
>> - Rename "notandnot" to "nor", document equivalence.
>> - Move comment cleanups to a separate patch.
>> - Use __always_inline.
>> ---
>> include/linux/find.h | 112 +++++++++++++++++++++++++++++++++++++++++++
>> lib/find_bit.c | 36 ++++++++++++++
>> 2 files changed, 148 insertions(+)
>>
>> diff --git a/include/linux/find.h b/include/linux/find.h
>> index 8a170aa55634..b1394ba92654 100644
>> --- a/include/linux/find.h
>> +++ b/include/linux/find.h
>> @@ -14,6 +14,8 @@ unsigned long _find_next_and_bit(const unsigned long *addr1, const unsigned long
>> unsigned long nbits, unsigned long start);
>> unsigned long _find_next_andnot_bit(const unsigned long *addr1, const unsigned long *addr2,
>> unsigned long nbits, unsigned long start);
>> +unsigned long _find_next_nor_bit(const unsigned long *addr1, const unsigned long *addr2,
>> + unsigned long nbits, unsigned long start);
>> unsigned long _find_next_or_bit(const unsigned long *addr1, const unsigned long *addr2,
>> unsigned long nbits, unsigned long start);
>> unsigned long _find_next_zero_bit(const unsigned long *addr, unsigned long nbits,
>> @@ -24,11 +26,17 @@ unsigned long __find_nth_and_bit(const unsigned long *addr1, const unsigned long
>> unsigned long size, unsigned long n);
>> unsigned long __find_nth_andnot_bit(const unsigned long *addr1, const unsigned long *addr2,
>> unsigned long size, unsigned long n);
>> +unsigned long __find_nth_nor_bit(const unsigned long *addr1, const unsigned long *addr2,
>> + unsigned long size, unsigned long n);
>> unsigned long __find_nth_and_andnot_bit(const unsigned long *addr1, const unsigned long *addr2,
>> const unsigned long *addr3, unsigned long size,
>> unsigned long n);
>> extern unsigned long _find_first_and_bit(const unsigned long *addr1,
>> const unsigned long *addr2, unsigned long size);
>> +extern unsigned long _find_first_andnot_bit(const unsigned long *addr1,
>> + const unsigned long *addr2, unsigned long size);
>> +extern unsigned long _find_first_nor_bit(const unsigned long *addr1,
>> + const unsigned long *addr2, unsigned long size);
>> unsigned long _find_first_and_and_bit(const unsigned long *addr1, const unsigned long *addr2,
>> const unsigned long *addr3, unsigned long size);
>> extern unsigned long _find_first_zero_bit(const unsigned long *addr, unsigned long size);
>> @@ -130,6 +138,35 @@ unsigned long find_next_andnot_bit(const unsigned long *addr1,
>> }
>> #endif
>>
>> +/**
>> + * find_next_nor_bit - find the next bit cleared in both *addr1 and *addr2
>> + * @addr1: The first address to base the search on
>> + * @addr2: The second address to base the search on
>> + * @size: The bitmap size in bits
>> + * @offset: The bitnumber to start searching at
>> + *
>> + * Returns the bit number for the next bit cleared in both *addr1 and *addr2.
>> + * If no such bits are found, returns @size.
>> + * The bitwise operation nor ~(A | B) is equivalent to (~A & ~B).
>> + */
>> +static __always_inline
>> +unsigned long find_next_nor_bit(const unsigned long *addr1,
>> + const unsigned long *addr2, unsigned long size,
>> + unsigned long offset)
>> +{
>> + if (small_const_nbits(size)) {
>> + unsigned long val;
>> +
>> + if (unlikely(offset >= size))
>> + return size;
>> +
>> + val = ~(*addr1 | *addr2) & GENMASK(size - 1, offset);
>> + return val ? __ffs(val) : size;
>> + }
>> +
>> + return _find_next_nor_bit(addr1, addr2, size, offset);
>> +}
>> +
>> #ifndef find_next_or_bit
>> /**
>> * find_next_or_bit - find the next set bit in either memory regions
>> @@ -291,6 +328,33 @@ unsigned long find_nth_andnot_bit(const unsigned long *addr1, const unsigned lon
>> return __find_nth_andnot_bit(addr1, addr2, size, n);
>> }
>>
>> +/**
>> + * find_nth_nor_bit - find N'th cleared bit in 2 memory regions.
>> + * @addr1: The 1st address to start the search at
>> + * @addr2: The 2nd address to start the search at
>> + * @size: The maximum number of bits to search
>> + * @n: The number of set bit, which position is needed, counting from 0
>> + *
>> + * Returns the bit number of the N'th bit cleared in the two regions.
>> + * If no such, returns @size.
>> + * The bitwise operation nor ~(A | B) is equivalent to (~A & ~B).
>> + */
>> +static __always_inline
>> +unsigned long find_nth_nor_bit(const unsigned long *addr1, const unsigned long *addr2,
>> + unsigned long size, unsigned long n)
>> +{
>> + if (n >= size)
>> + return size;
>> +
>> + if (small_const_nbits(size)) {
>> + unsigned long val = ~(*addr1 | *addr2) & GENMASK(size - 1, 0);
>> +
>> + return val ? fns(val, n) : size;
>> + }
>> +
>> + return __find_nth_nor_bit(addr1, addr2, size, n);
>> +}
>> +
>> /**
>> * find_nth_and_andnot_bit - find N'th set bit in 2 memory regions,
>> * excluding those set in 3rd region
>> @@ -346,6 +410,54 @@ unsigned long find_first_and_bit(const unsigned long *addr1,
>> }
>> #endif
>>
>> +/**
>> + * find_first_andnot_bit - find the first set bit in 2 memory regions,
>> + * flipping bits in 2nd region.
>> + * @addr1: The first address to base the search on
>> + * @addr2: The second address to base the search on
>> + * @size: The bitmap size in bits
>> + *
>> + * Returns the bit number for the next set bit.
>> + * If no bits are set, returns @size.
>> + */
>> +static __always_inline
>> +unsigned long find_first_andnot_bit(const unsigned long *addr1,
>> + const unsigned long *addr2,
>> + unsigned long size)
>> +{
>> + if (small_const_nbits(size)) {
>> + unsigned long val = *addr1 & (~*addr2) & GENMASK(size - 1, 0);
>> +
>> + return val ? __ffs(val) : size;
>> + }
>> +
>> + return _find_first_andnot_bit(addr1, addr2, size);
>> +}
>> +
>> +/**
>> + * find_first_nor_bit - find the first cleared bit in 2 memory regions
>> + * @addr1: The first address to base the search on
>> + * @addr2: The second address to base the search on
>> + * @size: The bitmap size in bits
>> + *
>> + * Returns the bit number for the next cleared bit.
>> + * If no bits are set, returns @size.
>> + * The bitwise operation nor ~(A | B) is equivalent to (~A & ~B).
>> + */
>> +static __always_inline
>> +unsigned long find_first_nor_bit(const unsigned long *addr1,
>> + const unsigned long *addr2,
>> + unsigned long size)
>> +{
>> + if (small_const_nbits(size)) {
>> + unsigned long val = ~(*addr1 | *addr2) & GENMASK(size - 1, 0);
>> +
>> + return val ? __ffs(val) : size;
>> + }
>> +
>> + return _find_first_nor_bit(addr1, addr2, size);
>> +}
>> +
>> /**
>> * find_first_and_and_bit - find the first set bit in 3 memory regions
>> * @addr1: The first address to base the search on
>> diff --git a/lib/find_bit.c b/lib/find_bit.c
>> index 0836bb3d76c5..8050bc7c7ede 100644
>> --- a/lib/find_bit.c
>> +++ b/lib/find_bit.c
>> @@ -116,6 +116,28 @@ unsigned long _find_first_and_bit(const unsigned long *addr1,
>> EXPORT_SYMBOL(_find_first_and_bit);
>> #endif
>>
>> +/*
>> + * Find the first set bit in two memory regions, flipping bits in 2nd region.
>> + */
>> +unsigned long _find_first_andnot_bit(const unsigned long *addr1,
>> + const unsigned long *addr2,
>> + unsigned long size)
>> +{
>> + return FIND_FIRST_BIT(addr1[idx] & ~addr2[idx], /* nop */, size);
>> +}
>> +EXPORT_SYMBOL(_find_first_andnot_bit);
>> +
>> +/*
>> + * Find the first cleared bit in two memory regions.
>> + */
>> +unsigned long _find_first_nor_bit(const unsigned long *addr1,
>> + const unsigned long *addr2,
>> + unsigned long size)
>> +{
>> + return FIND_FIRST_BIT(~(addr1[idx] | addr2[idx]), /* nop */, size);
>> +}
>> +EXPORT_SYMBOL(_find_first_nor_bit);
>> +
>> /*
>> * Find the first set bit in three memory regions.
>> */
>> @@ -167,6 +189,13 @@ unsigned long __find_nth_andnot_bit(const unsigned long *addr1, const unsigned l
>> }
>> EXPORT_SYMBOL(__find_nth_andnot_bit);
>>
>> +unsigned long __find_nth_nor_bit(const unsigned long *addr1, const unsigned long *addr2,
>> + unsigned long size, unsigned long n)
>> +{
>> + return FIND_NTH_BIT(~(addr1[idx] | addr2[idx]), size, n);
>> +}
>> +EXPORT_SYMBOL(__find_nth_nor_bit);
>> +
>> unsigned long __find_nth_and_andnot_bit(const unsigned long *addr1,
>> const unsigned long *addr2,
>> const unsigned long *addr3,
>> @@ -194,6 +223,13 @@ unsigned long _find_next_andnot_bit(const unsigned long *addr1, const unsigned l
>> EXPORT_SYMBOL(_find_next_andnot_bit);
>> #endif
>>
>> +unsigned long _find_next_nor_bit(const unsigned long *addr1, const unsigned long *addr2,
>> + unsigned long nbits, unsigned long start)
>> +{
>> + return FIND_NEXT_BIT(~(addr1[idx] | addr2[idx]), /* nop */, nbits, start);
>> +}
>> +EXPORT_SYMBOL(_find_next_nor_bit);
>> +
>> #ifndef find_next_or_bit
>> unsigned long _find_next_or_bit(const unsigned long *addr1, const unsigned long *addr2,
>> unsigned long nbits, unsigned long start)
>> --
>> 2.39.2
--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com
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