We don't need to use READ_ONCE() to read the map depth and word fields. This reduces overhead of __sbitmap_queue_get() dramatically on high IOPS devices, taking it from ~3% to a tenth of that.
Signed-off-by: Jens Axboe <[email protected]> --- lib/sbitmap.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/lib/sbitmap.c b/lib/sbitmap.c index fdd1b8aa8ac6..77442e04aeac 100644 --- a/lib/sbitmap.c +++ b/lib/sbitmap.c @@ -243,8 +243,8 @@ void sbitmap_bitmap_show(struct sbitmap *sb, struct seq_file *m) int i; for (i = 0; i < sb->map_nr; i++) { - unsigned long word = READ_ONCE(sb->map[i].word); - unsigned int word_bits = READ_ONCE(sb->map[i].depth); + unsigned long word = sb->map[i].word; + unsigned int word_bits = sb->map[i].depth; while (word_bits > 0) { unsigned int bits = min(8 - byte_bits, word_bits); @@ -375,7 +375,7 @@ int __sbitmap_queue_get(struct sbitmap_queue *sbq) int nr; hint = this_cpu_read(*sbq->alloc_hint); - depth = READ_ONCE(sbq->sb.depth); + depth = sbq->sb.depth; if (unlikely(hint >= depth)) { hint = depth ? prandom_u32() % depth : 0; this_cpu_write(*sbq->alloc_hint, hint); @@ -406,7 +406,7 @@ int __sbitmap_queue_get_shallow(struct sbitmap_queue *sbq, WARN_ON_ONCE(shallow_depth < sbq->min_shallow_depth); hint = this_cpu_read(*sbq->alloc_hint); - depth = READ_ONCE(sbq->sb.depth); + depth = sbq->sb.depth; if (unlikely(hint >= depth)) { hint = depth ? prandom_u32() % depth : 0; this_cpu_write(*sbq->alloc_hint, hint); -- 2.17.1 -- Jens Axboe
