From: Lin Feng linf@wangsu.com
[ Upstream commit 388c705b95f23f317fa43e6abf9ff07b583b721a ]
This reverts commit 6d4d273588378c65915acaf7b2ee74e9dd9c130a.
bfq.limit_depth passes word_depths[] as shallow_depth down to sbitmap core sbitmap_get_shallow, which uses just the number to limit the scan depth of each bitmap word, formula: scan_percentage_for_each_word = shallow_depth / (1 << sbimap->shift) * 100%
That means the comments's percentiles 50%, 75%, 18%, 37% of bfq are correct. But after commit patch 'bfq: Fix computation of shallow depth', we use sbitmap.depth instead, as a example in following case:
sbitmap.depth = 256, map_nr = 4, shift = 6; sbitmap_word.depth = 64. The resulsts of computed bfqd->word_depths[] are {128, 192, 48, 96}, and three of the numbers exceed core dirver's 'sbitmap_word.depth=64' limit nothing.
Signed-off-by: Lin Feng linf@wangsu.com Reviewed-by: Jan Kara jack@suse.cz Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- block/bfq-iosched.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index 9e4eb0fc1c16e..9e81d1052091f 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -6332,13 +6332,13 @@ static unsigned int bfq_update_depths(struct bfq_data *bfqd, * limit 'something'. */ /* no more than 50% of tags for async I/O */ - bfqd->word_depths[0][0] = max(bt->sb.depth >> 1, 1U); + bfqd->word_depths[0][0] = max((1U << bt->sb.shift) >> 1, 1U); /* * no more than 75% of tags for sync writes (25% extra tags * w.r.t. async I/O, to prevent async I/O from starving sync * writes) */ - bfqd->word_depths[0][1] = max((bt->sb.depth * 3) >> 2, 1U); + bfqd->word_depths[0][1] = max(((1U << bt->sb.shift) * 3) >> 2, 1U);
/* * In-word depths in case some bfq_queue is being weight- @@ -6348,9 +6348,9 @@ static unsigned int bfq_update_depths(struct bfq_data *bfqd, * shortage. */ /* no more than ~18% of tags for async I/O */ - bfqd->word_depths[1][0] = max((bt->sb.depth * 3) >> 4, 1U); + bfqd->word_depths[1][0] = max(((1U << bt->sb.shift) * 3) >> 4, 1U); /* no more than ~37% of tags for sync writes (~20% extra tags) */ - bfqd->word_depths[1][1] = max((bt->sb.depth * 6) >> 4, 1U); + bfqd->word_depths[1][1] = max(((1U << bt->sb.shift) * 6) >> 4, 1U);
for (i = 0; i < 2; i++) for (j = 0; j < 2; j++)