On Tue, Oct 29, 2019 at 12:19:04PM +0800, 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>
> ---
> 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);
We have users of adding multiple pages in single bio_add_page(),
will fix it in V2.
Thanks,
Ming
