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lib/sbitmap: kill 'depth' from sbitmap_word 

Only the last sbitmap_word can have different depth, and all the others
must have same depth of 1U << sb->shift, so not necessary to store it in
sbitmap_word, and it can be retrieved easily and efficiently by adding
one internal helper of __map_depth(sb, index).

Remove 'depth' field from sbitmap_word, then the annotation of
____cacheline_aligned_in_smp for 'word' isn't needed any more.

Not see performance effect when running high parallel IOPS test on
null_blk.

This way saves us one cacheline(usually 64 words) per each sbitmap_word.

Cc: Martin Wilck <martin.wilck@suse.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Martin Wilck <mwilck@suse.com>
Reviewed-by: John Garry <john.garry@huawei.com>
Link: https://lore.kernel.org/r/20220110072945.347535-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Ming Lei 2022-01-10 15:29:45 +08:00 committed by Jens Axboe
parent abfc426d1b
commit 3301bc5335
2 changed files with 24 additions and 27 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
include/linux/sbitmap.h
View File

@ -27,15 +27,10 @@ struct seq_file;
* struct sbitmap_word - Word in a &struct sbitmap.
*/
struct sbitmap_word {
/**
* @depth: Number of bits being used in @word/@cleared
*/
unsigned long depth;
/**
* @word: word holding free bits
*/
unsigned long word ____cacheline_aligned_in_smp;
unsigned long word;
/**
* @cleared: word holding cleared bits
@ -164,6 +159,14 @@ struct sbitmap_queue {
int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
gfp_t flags, int node, bool round_robin, bool alloc_hint);
/* sbitmap internal helper */
static inline unsigned int __map_depth(const struct sbitmap *sb, int index)
{
if (index == sb->map_nr - 1)
return sb->depth - (index << sb->shift);
return 1U << sb->shift;
}
/**
* sbitmap_free() - Free memory used by a &struct sbitmap.
* @sb: Bitmap to free.
@ -251,7 +254,7 @@ static inline void __sbitmap_for_each_set(struct sbitmap *sb,
while (scanned < sb->depth) {
unsigned long word;
unsigned int depth = min_t(unsigned int,
sb->map[index].depth - nr,
__map_depth(sb, index) - nr,
sb->depth - scanned);
scanned += depth;

34
lib/sbitmap.c
View File

@ -85,7 +85,6 @@ int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
bool alloc_hint)
{
unsigned int bits_per_word;
unsigned int i;
if (shift < 0)
shift = sbitmap_calculate_shift(depth);
@ -117,10 +116,6 @@ int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
return -ENOMEM;
}
for (i = 0; i < sb->map_nr; i++) {
sb->map[i].depth = min(depth, bits_per_word);
depth -= sb->map[i].depth;
}
return 0;
}
EXPORT_SYMBOL_GPL(sbitmap_init_node);
@ -135,11 +130,6 @@ void sbitmap_resize(struct sbitmap *sb, unsigned int depth)
sb->depth = depth;
sb->map_nr = DIV_ROUND_UP(sb->depth, bits_per_word);
for (i = 0; i < sb->map_nr; i++) {
sb->map[i].depth = min(depth, bits_per_word);
depth -= sb->map[i].depth;
}
}
EXPORT_SYMBOL_GPL(sbitmap_resize);
@ -184,8 +174,8 @@ static int sbitmap_find_bit_in_index(struct sbitmap *sb, int index,
int nr;
do {
nr = __sbitmap_get_word(&map->word, map->depth, alloc_hint,
!sb->round_robin);
nr = __sbitmap_get_word(&map->word, __map_depth(sb, index),
alloc_hint, !sb->round_robin);
if (nr != -1)
break;
if (!sbitmap_deferred_clear(map))
@ -257,7 +247,9 @@ static int __sbitmap_get_shallow(struct sbitmap *sb,
for (i = 0; i < sb->map_nr; i++) {
again:
nr = __sbitmap_get_word(&sb->map[index].word,
min(sb->map[index].depth, shallow_depth),
min_t(unsigned int,
__map_depth(sb, index),
shallow_depth),
SB_NR_TO_BIT(sb, alloc_hint), true);
if (nr != -1) {
nr += index << sb->shift;
@ -315,11 +307,12 @@ static unsigned int __sbitmap_weight(const struct sbitmap *sb, bool set)
for (i = 0; i < sb->map_nr; i++) {
const struct sbitmap_word *word = &sb->map[i];
unsigned int word_depth = __map_depth(sb, i);
if (set)
weight += bitmap_weight(&word->word, word->depth);
weight += bitmap_weight(&word->word, word_depth);
else
weight += bitmap_weight(&word->cleared, word->depth);
weight += bitmap_weight(&word->cleared, word_depth);
}
return weight;
}
@ -367,7 +360,7 @@ void sbitmap_bitmap_show(struct sbitmap *sb, struct seq_file *m)
for (i = 0; i < sb->map_nr; i++) {
unsigned long word = READ_ONCE(sb->map[i].word);
unsigned long cleared = READ_ONCE(sb->map[i].cleared);
unsigned int word_bits = READ_ONCE(sb->map[i].depth);
unsigned int word_bits = __map_depth(sb, i);
word &= ~cleared;
@ -531,15 +524,16 @@ unsigned long __sbitmap_queue_get_batch(struct sbitmap_queue *sbq, int nr_tags,
for (i = 0; i < sb->map_nr; i++) {
struct sbitmap_word *map = &sb->map[index];
unsigned long get_mask;
unsigned int map_depth = __map_depth(sb, index);
sbitmap_deferred_clear(map);
if (map->word == (1UL << (map->depth - 1)) - 1)
if (map->word == (1UL << (map_depth - 1)) - 1)
continue;
nr = find_first_zero_bit(&map->word, map->depth);
if (nr + nr_tags <= map->depth) {
nr = find_first_zero_bit(&map->word, map_depth);
if (nr + nr_tags <= map_depth) {
atomic_long_t *ptr = (atomic_long_t *) &map->word;
int map_tags = min_t(int, nr_tags, map->depth);
int map_tags = min_t(int, nr_tags, map_depth);
unsigned long val, ret;
get_mask = ((1UL << map_tags) - 1) << nr;