linux.git/lib/bitmap.c, branch v7.1-rc2

bitmap: introduce bitmap_weighted_xor()

2026-04-02T00:03:07+00:00

The function helps to XOR bitmaps and calculate Hamming weight of
the result in one pass.

Reviewed-by: Aleksandr Loktionov 
Reviewed-by: Jacob Keller 
Signed-off-by: Yury Norov

bitmap: add test_zero_nbits()

2026-03-24T17:39:53+00:00

In most real-life cases, 0-length bitmap provided by user is a sign of
an error. The API doesn't provide any guarantees on returned value, and
the bitmap pointers are not dereferenced.

Signed-off-by: Yury Norov

cpumask: Introduce cpumask_weighted_or()

2025-11-20T11:14:54+00:00

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 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Yury Norov (NVIDIA) 
Reviewed-by: Mathieu Desnoyers 
Link: https://patch.msgid.link/20251119172549.448263340@linutronix.de

cpumask: add cpumask_weight_andnot()

2024-02-01T12:06:40+00:00

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 
Reviewed-by: Jacob Keller 
Signed-off-by: Paolo Abeni

bitmap: move bitmap_*_region() functions to bitmap.h

2023-10-16T23:14:45+00:00

Now that bitmap_*_region() functions are implemented as thin wrappers
around others, it's worth to move them to the header, as it opens room
for compile-time optimizations.

CC: Andy Shevchenko 
CC: Rasmus Villemoes 
CC: Greg Kroah-Hartman 
Signed-off-by: Yury Norov

bitmap: drop _reg_op() function

2023-10-15T03:25:23+00:00

Now that all _reg_op() users are switched to alternative functions,
_reg_op() machinery is not needed anymore.

CC: Andy Shevchenko 
CC: Rasmus Villemoes 
Signed-off-by: Yury Norov

bitmap: replace _reg_op(REG_OP_ISFREE) with find_next_bit()

2023-10-15T03:25:22+00:00

_reg_op(REG_OP_ISFREE) can be trivially replaced with find_next_bit().
Doing that opens room for potential small_const_nbits() optimization.

CC: Andy Shevchenko 
CC: Rasmus Villemoes 
Signed-off-by: Yury Norov

bitmap: replace _reg_op(REG_OP_RELEASE) with bitmap_clear()

2023-10-15T03:25:22+00:00

_reg_op(REG_OP_RELEASE) duplicates bitmap_clear().

CC: Andy Shevchenko 
CC: Rasmus Villemoes 
Signed-off-by: Yury Norov

bitmap: replace _reg_op(REG_OP_ALLOC) with bitmap_set()

2023-10-15T03:25:22+00:00

_reg_op(REG_OP_ALLOC) duplicates bitmap_set().

CC: Andy Shevchenko 
CC: Rasmus Villemoes 
Signed-off-by: Yury Norov

bitmap: fix opencoded bitmap_allocate_region()

2023-10-15T03:25:22+00:00

bitmap_find_region() opencodes bitmap_allocate_region().

CC: Andy Shevchenko 
CC: Rasmus Villemoes 
Signed-off-by: Yury Norov