Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
bitmap: generalize node_random()
Generalize node_random() and make it available to general bitmaps and
cpumasks users.
Notice, find_first_bit() is generally faster than find_nth_bit(), and we
employ it when there's a single set bit in the bitmap.
See commit 3e061d924fe9c7b4 ("lib/nodemask: optimize node_random for
nodemask with single NUMA node").
CC: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: "Yury Norov [NVIDIA]" <yury.norov@gmail.com>
+28
-14
+2
include/linux/find.h
+2
include/linux/find.h
+2
-14
include/linux/nodemask.h
+2
-14
include/linux/nodemask.h
···
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static __always_inline int node_random(const nodemask_t *maskp)
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{
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#if defined(CONFIG_NUMA) && (MAX_NUMNODES > 1)
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-
int w, bit;
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+
int node = find_random_bit(maskp->bits, MAX_NUMNODES);
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-
w = nodes_weight(*maskp);
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-
switch (w) {
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case 0:
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bit = NUMA_NO_NODE;
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break;
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case 1:
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bit = first_node(*maskp);
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break;
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default:
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bit = find_nth_bit(maskp->bits, MAX_NUMNODES, get_random_u32_below(w));
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break;
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}
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return bit;
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return node < MAX_NUMNODES ? node : NUMA_NO_NODE;
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#else
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return 0;
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#endif
+24
lib/find_bit.c
+24
lib/find_bit.c
···
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#include <linux/math.h>
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#include <linux/minmax.h>
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#include <linux/swab.h>
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#include <linux/random.h>
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/*
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* Common helper for find_bit() function family
···
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#endif
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#endif /* __BIG_ENDIAN */
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+
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/**
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* find_random_bit - find a set bit at random position
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* @addr: The address to base the search on
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* @size: The bitmap size in bits
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*
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* Returns: a position of a random set bit; >= @size otherwise
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*/
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unsigned long find_random_bit(const unsigned long *addr, unsigned long size)
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{
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int w = bitmap_weight(addr, size);
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+
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switch (w) {
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case 0:
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return size;
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case 1:
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/* Performance trick for single-bit bitmaps */
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return find_first_bit(addr, size);
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default:
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return find_nth_bit(addr, size, get_random_u32_below(w));
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}
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}
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+
EXPORT_SYMBOL(find_random_bit);