2018-11-07 13:59:27

by Johannes Thumshirn

Subject: [PATCH v2] block: respect virtual boundary mask in bvecs

With drivers that are settting a virtual boundary constrain, we are
seeing a lot of bio splitting and smaller I/Os being submitted to the
driver.

This happens because the bio gap detection code does not account cases
where PAGE_SIZE - 1 is bigger than queue_virt_boundary() and thus will
split the bio unnecessarily.

Cc: Jan Kara <[email protected]>
Cc: Sagi Grimberg <[email protected]>
Cc: Bart Van Assche <[email protected]>
Cc: Ming Lei <[email protected]>
Signed-off-by: Johannes Thumshirn <[email protected]>
Acked-by: Keith Busch <[email protected]>
Reviewed-by: Ming Lei <[email protected]>

---
Changes to v1:
* Tried to re-phrase the commit message
* Add reviews
---
block/blk-merge.c | 2 +-
block/blk.h | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/block/blk-merge.c b/block/blk-merge.c
index 6b5ad275ed56..208658a901c6 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -46,7 +46,7 @@ static inline bool bio_will_gap(struct request_queue *q,
bio_get_first_bvec(prev_rq->bio, &pb);
else
bio_get_first_bvec(prev, &pb);
- if (pb.bv_offset)
+ if (pb.bv_offset & queue_virt_boundary(q))
return true;

/*
diff --git a/block/blk.h b/block/blk.h
index a1841b8ff129..c85e53f21cdd 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -169,7 +169,7 @@ static inline bool biovec_phys_mergeable(struct request_queue *q,
static inline bool __bvec_gap_to_prev(struct request_queue *q,
struct bio_vec *bprv, unsigned int offset)
{
- return offset ||
+ return (offset & queue_virt_boundary(q)) ||
((bprv->bv_offset + bprv->bv_len) & queue_virt_boundary(q));
}

--
2.16.4

2018-11-07 18:32:32

by Sagi Grimberg

Subject: Re: [PATCH v2] block: respect virtual boundary mask in bvecs

Reviewed-by: Sagi Grimberg <[email protected]>

2018-11-07 20:06:36

by Jens Axboe

Subject: Re: [PATCH v2] block: respect virtual boundary mask in bvecs

On 11/7/18 6:58 AM, Johannes Thumshirn wrote:
> With drivers that are settting a virtual boundary constrain, we are
> seeing a lot of bio splitting and smaller I/Os being submitted to the
> driver.
>
> This happens because the bio gap detection code does not account cases
> where PAGE_SIZE - 1 is bigger than queue_virt_boundary() and thus will
> split the bio unnecessarily.

Thanks, applied.

--
Jens Axboe

2018-11-07 20:08:31

by Jens Axboe

Subject: Re: [PATCH v2] block: respect virtual boundary mask in bvecs

On 11/7/18 6:58 AM, Johannes Thumshirn wrote:
> With drivers that are settting a virtual boundary constrain, we are
> seeing a lot of bio splitting and smaller I/Os being submitted to the
> driver.
>
> This happens because the bio gap detection code does not account cases
> where PAGE_SIZE - 1 is bigger than queue_virt_boundary() and thus will
> split the bio unnecessarily.

Thanks, applied.

--
Jens Axboe