From 27fae429acee1e9418059e7fa545438075af5256 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Thu, 29 Nov 2018 12:35:16 -0700 Subject: sbitmap: don't loop for find_next_zero_bit() for !round_robin If we aren't forced to do round robin tag allocation, just use the allocation hint to find the index for the tag word, don't use it for the offset inside the word. This avoids a potential extra round trip in the bit looping, and since we're fetching this cacheline, we may as well check the whole word from the start. Reviewed-by: Omar Sandoval Signed-off-by: Jens Axboe --- lib/sbitmap.c | 21 +++++++++++++-------- 1 file changed, 13 insertions(+), 8 deletions(-) (limited to 'lib/sbitmap.c') diff --git a/lib/sbitmap.c b/lib/sbitmap.c index fdd1b8aa8ac6..45cab6bbc1c7 100644 --- a/lib/sbitmap.c +++ b/lib/sbitmap.c @@ -118,10 +118,19 @@ int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint, bool round_robin) index = SB_NR_TO_INDEX(sb, alloc_hint); + /* + * Unless we're doing round robin tag allocation, just use the + * alloc_hint to find the right word index. No point in looping + * twice in find_next_zero_bit() for that case. + */ + if (round_robin) + alloc_hint = SB_NR_TO_BIT(sb, alloc_hint); + else + alloc_hint = 0; + for (i = 0; i < sb->map_nr; i++) { nr = __sbitmap_get_word(&sb->map[index].word, - sb->map[index].depth, - SB_NR_TO_BIT(sb, alloc_hint), + sb->map[index].depth, alloc_hint, !round_robin); if (nr != -1) { nr += index << sb->shift; @@ -129,13 +138,9 @@ int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint, bool round_robin) } /* Jump to next index. */ - index++; - alloc_hint = index << sb->shift; - - if (index >= sb->map_nr) { + alloc_hint = 0; + if (++index >= sb->map_nr) index = 0; - alloc_hint = 0; - } } return nr; -- cgit