On 2019/10/29 12:19 下午, Ming Lei wrote:
> __blk_queue_split() may be a bit heavy for small BS(such as 512B, or
> 4KB) IO, so introduce one flag to decide if this bio includes multiple
> page. And only consider to try splitting this bio in case that
> the multiple page flag is set.
>
> ~3% - 5% IOPS improvement can be observed on io_uring test over
> null_blk(MQ), and the io_uring test code is from fio/t/io_uring.c
>
> bch_bio_map() should be the only one which doesn't use bio_add_page(),
> so force to mark bio built via bch_bio_map() as MULTI_PAGE.
>
> RAID5 has similar usage too, however the bio is really single-page bio,
> so not necessary to handle it.
>
> Cc: Coly Li <colyli@xxxxxxx>
> Cc: linux-bcache@xxxxxxxxxxxxxxx
> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
Hi Ming,
For the bcache part, it is OK for me.
Acked-by: Coly Li <colyli@xxxxxxx>
Thanks.
Coly Li
> ---
> block/bio.c | 8 ++++++++
> block/blk-merge.c | 4 ++++
> block/bounce.c | 3 +++
> drivers/md/bcache/util.c | 2 ++
> include/linux/blk_types.h | 1 +
> 5 files changed, 18 insertions(+)
>
> diff --git a/block/bio.c b/block/bio.c
> index 8f0ed6228fc5..c288364b7cf3 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -583,6 +583,8 @@ void __bio_clone_fast(struct bio *bio, struct bio *bio_src)
> bio_set_flag(bio, BIO_CLONED);
> if (bio_flagged(bio_src, BIO_THROTTLED))
> bio_set_flag(bio, BIO_THROTTLED);
> + if (bio_flagged(bio_src, BIO_MULTI_PAGE))
> + bio_set_flag(bio, BIO_MULTI_PAGE);
> bio->bi_opf = bio_src->bi_opf;
> bio->bi_ioprio = bio_src->bi_ioprio;
> bio->bi_write_hint = bio_src->bi_write_hint;
> @@ -757,6 +759,9 @@ bool __bio_try_merge_page(struct bio *bio, struct page *page,
> if (page_is_mergeable(bv, page, len, off, same_page)) {
> bv->bv_len += len;
> bio->bi_iter.bi_size += len;
> +
> + if (!*same_page)
> + bio_set_flag(bio, BIO_MULTI_PAGE);
> return true;
> }
> }
> @@ -789,6 +794,9 @@ void __bio_add_page(struct bio *bio, struct page *page,
> bio->bi_iter.bi_size += len;
> bio->bi_vcnt++;
>
> + if (bio->bi_vcnt >= 2 && !bio_flagged(bio, BIO_MULTI_PAGE))
> + bio_set_flag(bio, BIO_MULTI_PAGE);
> +
> if (!bio_flagged(bio, BIO_WORKINGSET) && unlikely(PageWorkingset(page)))
> bio_set_flag(bio, BIO_WORKINGSET);
> }
> diff --git a/block/blk-merge.c b/block/blk-merge.c
> index 48e6725b32ee..737bbec9e153 100644
> --- a/block/blk-merge.c
> +++ b/block/blk-merge.c
> @@ -309,6 +309,10 @@ void __blk_queue_split(struct request_queue *q, struct bio **bio,
> nr_segs);
> break;
> default:
> + if (!bio_flagged(*bio, BIO_MULTI_PAGE)) {
> + *nr_segs = 1;
> + return;
> + }
> split = blk_bio_segment_split(q, *bio, &q->bio_split, nr_segs);
> break;
> }
> diff --git a/block/bounce.c b/block/bounce.c
> index f8ed677a1bf7..4b18a2accccc 100644
> --- a/block/bounce.c
> +++ b/block/bounce.c
> @@ -253,6 +253,9 @@ static struct bio *bounce_clone_bio(struct bio *bio_src, gfp_t gfp_mask,
> bio->bi_iter.bi_sector = bio_src->bi_iter.bi_sector;
> bio->bi_iter.bi_size = bio_src->bi_iter.bi_size;
>
> + if (bio_flagged(bio_src, BIO_MULTI_PAGE))
> + bio_set_flag(bio, BIO_MULTI_PAGE);
> +
> switch (bio_op(bio)) {
> case REQ_OP_DISCARD:
> case REQ_OP_SECURE_ERASE:
> diff --git a/drivers/md/bcache/util.c b/drivers/md/bcache/util.c
> index 62fb917f7a4f..71f5cbb6fdd6 100644
> --- a/drivers/md/bcache/util.c
> +++ b/drivers/md/bcache/util.c
> @@ -253,6 +253,8 @@ start: bv->bv_len = min_t(size_t, PAGE_SIZE - bv->bv_offset,
>
> size -= bv->bv_len;
> }
> +
> + bio_set_flag(bio, BIO_MULTI_PAGE);
> }
>
> /**
> diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
> index d688b96d1d63..b942399c97a0 100644
> --- a/include/linux/blk_types.h
> +++ b/include/linux/blk_types.h
> @@ -222,6 +222,7 @@ enum {
> * of this bio. */
> BIO_QUEUE_ENTERED, /* can use blk_queue_enter_live() */
> BIO_TRACKED, /* set if bio goes through the rq_qos path */
> + BIO_MULTI_PAGE, /* used for optimize small BS IO */
> BIO_FLAG_LAST
> };
>
