Introduce a fast path for single-page bvec IO, then blk_bvec_map_sg() can be avoided.
Signed-off-by: Ming Lei <[email protected]> --- block/blk-merge.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/block/blk-merge.c b/block/blk-merge.c index c7e8a8273460..c1ad8abbd9d6 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -447,7 +447,7 @@ static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio, return biovec_phys_mergeable(q, &end_bv, &nxt_bv); } -static struct scatterlist *blk_next_sg(struct scatterlist **sg, +static inline struct scatterlist *blk_next_sg(struct scatterlist **sg, struct scatterlist *sglist) { if (!*sg) @@ -512,7 +512,12 @@ __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, (*sg)->length += nbytes; } else { new_segment: - (*nsegs) += blk_bvec_map_sg(q, bvec, sglist, sg); + if (bvec->bv_offset + bvec->bv_len <= PAGE_SIZE) { + *sg = blk_next_sg(sg, sglist); + sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset); + (*nsegs) += 1; + } else + (*nsegs) += blk_bvec_map_sg(q, bvec, sglist, sg); } *bvprv = *bvec; } -- 2.9.5
