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authorKeith Busch <keith.busch@intel.com>2016-01-12 15:08:39 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-02-17 12:30:55 -0800
commitd2081cfe624b5decaaf68088ca256ed1b140672c (patch)
tree1f32156f62d42a5aa439a9b298b3c44ec5e43181 /block/blk-merge.c
parent1f1c9c9befd45d61ff0a91ea78892be03a4087e7 (diff)
block: split bios to max possible length
commit e36f6204288088fda50d1c84830340ccb70f85ff upstream. This splits bio in the middle of a vector to form the largest possible bio at the h/w's desired alignment, and guarantees the bio being split will have some data. The criteria for splitting is changed from the max sectors to the h/w's optimal sector alignment if it is provided. For h/w that advertise their block storage's underlying chunk size, it's a big performance win to not submit commands that cross them. If sector alignment is not provided, this patch uses the max sectors as before. This addresses the performance issue commit d380561113 attempted to fix, but was reverted due to splitting logic error. Signed-off-by: Keith Busch <keith.busch@intel.com> Cc: Jens Axboe <axboe@fb.com> Cc: Ming Lei <tom.leiming@gmail.com> Cc: Kent Overstreet <kent.overstreet@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'block/blk-merge.c')
-rw-r--r--block/blk-merge.c19
1 files changed, 16 insertions, 3 deletions
diff --git a/block/blk-merge.c b/block/blk-merge.c
index e01405a3e8b3..6b982cacaea8 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -81,9 +81,6 @@ static struct bio *blk_bio_segment_split(struct request_queue *q,
struct bio *new = NULL;
bio_for_each_segment(bv, bio, iter) {
- if (sectors + (bv.bv_len >> 9) > queue_max_sectors(q))
- goto split;
-
/*
* If the queue doesn't support SG gaps and adding this
* offset would create a gap, disallow it.
@@ -91,6 +88,22 @@ static struct bio *blk_bio_segment_split(struct request_queue *q,
if (bvprvp && bvec_gap_to_prev(q, bvprvp, bv.bv_offset))
goto split;
+ if (sectors + (bv.bv_len >> 9) >
+ blk_max_size_offset(q, bio->bi_iter.bi_sector)) {
+ /*
+ * Consider this a new segment if we're splitting in
+ * the middle of this vector.
+ */
+ if (nsegs < queue_max_segments(q) &&
+ sectors < blk_max_size_offset(q,
+ bio->bi_iter.bi_sector)) {
+ nsegs++;
+ sectors = blk_max_size_offset(q,
+ bio->bi_iter.bi_sector);
+ }
+ goto split;
+ }
+
if (bvprvp && blk_queue_cluster(q)) {
if (seg_size + bv.bv_len > queue_max_segment_size(q))
goto new_segment;