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authorPavel Begunkov <asml.silence@gmail.com>2020-11-22 15:35:45 +0000
committerJens Axboe <axboe@kernel.dk>2020-12-07 17:12:49 -0700
commitb78beea038a3087df63bba7adaacb476a8ca95af (patch)
tree296886e70357e7c8b78718e3604126d4867c1e0e
parentf6f371f7db42917c7b2a861c4fc923cb352ce5a1 (diff)
sbitmap: optimise sbitmap_deferred_clear()
Because of spinlocks and atomics sbitmap_deferred_clear() have to reload &sb->map[index] on each access even though the map address won't change. Pass in sbitmap_word instead of {sb, index}, so it's cached in a variable. It also improves code generation of sbitmap_find_bit_in_index(). Signed-off-by: Pavel Begunkov <asml.silence@gmail.com> Reviewed-by: John Garry <john.garry@huawei.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
-rw-r--r--lib/sbitmap.c24
1 files changed, 12 insertions, 12 deletions
diff --git a/lib/sbitmap.c b/lib/sbitmap.c
index 267aa7709416..c1c8a4e69325 100644
--- a/lib/sbitmap.c
+++ b/lib/sbitmap.c
@@ -12,32 +12,32 @@
/*
* See if we have deferred clears that we can batch move
*/
-static inline bool sbitmap_deferred_clear(struct sbitmap *sb, int index)
+static inline bool sbitmap_deferred_clear(struct sbitmap_word *map)
{
unsigned long mask, val;
bool ret = false;
unsigned long flags;
- spin_lock_irqsave(&sb->map[index].swap_lock, flags);
+ spin_lock_irqsave(&map->swap_lock, flags);
- if (!sb->map[index].cleared)
+ if (!map->cleared)
goto out_unlock;
/*
* First get a stable cleared mask, setting the old mask to 0.
*/
- mask = xchg(&sb->map[index].cleared, 0);
+ mask = xchg(&map->cleared, 0);
/*
* Now clear the masked bits in our free word
*/
do {
- val = sb->map[index].word;
- } while (cmpxchg(&sb->map[index].word, val, val & ~mask) != val);
+ val = map->word;
+ } while (cmpxchg(&map->word, val, val & ~mask) != val);
ret = true;
out_unlock:
- spin_unlock_irqrestore(&sb->map[index].swap_lock, flags);
+ spin_unlock_irqrestore(&map->swap_lock, flags);
return ret;
}
@@ -92,7 +92,7 @@ void sbitmap_resize(struct sbitmap *sb, unsigned int depth)
unsigned int i;
for (i = 0; i < sb->map_nr; i++)
- sbitmap_deferred_clear(sb, i);
+ sbitmap_deferred_clear(&sb->map[i]);
sb->depth = depth;
sb->map_nr = DIV_ROUND_UP(sb->depth, bits_per_word);
@@ -139,15 +139,15 @@ static int __sbitmap_get_word(unsigned long *word, unsigned long depth,
static int sbitmap_find_bit_in_index(struct sbitmap *sb, int index,
unsigned int alloc_hint, bool round_robin)
{
+ struct sbitmap_word *map = &sb->map[index];
int nr;
do {
- nr = __sbitmap_get_word(&sb->map[index].word,
- sb->map[index].depth, alloc_hint,
+ nr = __sbitmap_get_word(&map->word, map->depth, alloc_hint,
!round_robin);
if (nr != -1)
break;
- if (!sbitmap_deferred_clear(sb, index))
+ if (!sbitmap_deferred_clear(map))
break;
} while (1);
@@ -207,7 +207,7 @@ again:
break;
}
- if (sbitmap_deferred_clear(sb, index))
+ if (sbitmap_deferred_clear(&sb->map[index]))
goto again;
/* Jump to next index. */