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cpumask: Introduce cpumask_weighted_or()

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CID management OR's two cpumasks and then calculates the weight on the
result. That's inefficient as that has to walk the same stuff twice. As
this is done with runqueue lock held, there is a real benefit of speeding
this up. Depending on the system this results in 10-20% less cycles spent
with runqueue lock held for a 4K cpumask.

Provide cpumask_weighted_or() and the corresponding bitmap functions which
return the weight of the OR result right away.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://patch.msgid.link/20251119172549.448263340@linutronix.de
This commit is contained in:
Thomas Gleixner
2025-11-19 18:26:57 +01:00
committed by Peter Zijlstra
parent 0d032a43eb
commit 437cb3ded2
3 changed files with 37 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

15
include/linux/bitmap.h
View File

@@ -45,6 +45,7 @@ struct device;
* bitmap_copy(dst, src, nbits) *dst = *src
* bitmap_and(dst, src1, src2, nbits) *dst = *src1 & *src2
* bitmap_or(dst, src1, src2, nbits) *dst = *src1 | *src2
* bitmap_weighted_or(dst, src1, src2, nbits) *dst = *src1 | *src2. Returns Hamming Weight of dst
* bitmap_xor(dst, src1, src2, nbits) *dst = *src1 ^ *src2
* bitmap_andnot(dst, src1, src2, nbits) *dst = *src1 & ~(*src2)
* bitmap_complement(dst, src, nbits) *dst = ~(*src)
@@ -165,6 +166,8 @@ bool __bitmap_and(unsigned long *dst, const unsigned long *bitmap1,
const unsigned long *bitmap2, unsigned int nbits);
void __bitmap_or(unsigned long *dst, const unsigned long *bitmap1,
const unsigned long *bitmap2, unsigned int nbits);
unsigned int __bitmap_weighted_or(unsigned long *dst, const unsigned long *bitmap1,
const unsigned long *bitmap2, unsigned int nbits);
void __bitmap_xor(unsigned long *dst, const unsigned long *bitmap1,
const unsigned long *bitmap2, unsigned int nbits);
bool __bitmap_andnot(unsigned long *dst, const unsigned long *bitmap1,
@@ -337,6 +340,18 @@ void bitmap_or(unsigned long *dst, const unsigned long *src1,
__bitmap_or(dst, src1, src2, nbits);
}
static __always_inline
unsigned int bitmap_weighted_or(unsigned long *dst, const unsigned long *src1,
const unsigned long *src2, unsigned int nbits)
{
if (small_const_nbits(nbits)) {
*dst = *src1 | *src2;
return hweight_long(*dst & BITMAP_LAST_WORD_MASK(nbits));
} else {
return __bitmap_weighted_or(dst, src1, src2, nbits);
}
}
static __always_inline
void bitmap_xor(unsigned long *dst, const unsigned long *src1,
const unsigned long *src2, unsigned int nbits)

16
include/linux/cpumask.h
View File

@@ -728,6 +728,22 @@ void cpumask_or(struct cpumask *dstp, const struct cpumask *src1p,
cpumask_bits(src2p), small_cpumask_bits);
}
/**
* cpumask_weighted_or - *dstp = *src1p | *src2p and return the weight of the result
* @dstp: the cpumask result
* @src1p: the first input
* @src2p: the second input
*
* Return: The number of bits set in the resulting cpumask @dstp
*/
static __always_inline
unsigned int cpumask_weighted_or(struct cpumask *dstp, const struct cpumask *src1p,
const struct cpumask *src2p)
{
return bitmap_weighted_or(cpumask_bits(dstp), cpumask_bits(src1p),
cpumask_bits(src2p), small_cpumask_bits);
}
/**
* cpumask_xor - *dstp = *src1p ^ *src2p
* @dstp: the cpumask result

6
lib/bitmap.c
View File

@@ -355,6 +355,12 @@ unsigned int __bitmap_weight_andnot(const unsigned long *bitmap1,
}
EXPORT_SYMBOL(__bitmap_weight_andnot);
unsigned int __bitmap_weighted_or(unsigned long *dst, const unsigned long *bitmap1,
const unsigned long *bitmap2, unsigned int bits)
{
return BITMAP_WEIGHT(({dst[idx] = bitmap1[idx] | bitmap2[idx]; dst[idx]; }), bits);
}
void __bitmap_set(unsigned long *map, unsigned int start, int len)
{
unsigned long *p = map + BIT_WORD(start);