summaryrefslogtreecommitdiff
path: root/block
diff options
context:
space:
mode:
authorKeith Busch <keith.busch@intel.com>2016-01-12 15:08:39 -0700
committerJens Axboe <axboe@fb.com>2016-01-12 15:10:56 -0700
commite36f6204288088fda50d1c84830340ccb70f85ff (patch)
tree58665774f3a1569b45b80346f8ff782d6a053443 /block
parentcda22646adaa453519fac28222f20b0d73aa8562 (diff)
downloadlinux-sh-e36f6204288088fda50d1c84830340ccb70f85ff.tar.gz
block: split bios to max possible length
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> Cc: <stable@vger.kernel.org> # 4.4.x- Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'block')
-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 0e5643a5d1c3..237b087d3529 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -83,9 +83,6 @@ 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.
@@ -93,6 +90,22 @@ 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;