Re: [RESEND PATCH v5 1/2] bio: limit bio max size
On Wed, Apr 07, 2021 at 03:55:07PM +0900, Changheun Lee wrote:
> > On Wed, Apr 07, 2021 at 02:06:33PM +0900, Changheun Lee wrote:
> > > > On Wed, Apr 07, 2021 at 09:16:12AM +0900, Changheun Lee wrote:
> > > > > > On Tue, Apr 06, 2021 at 10:31:28AM +0900, Changheun Lee wrote:
> > > > > > > > bio size can grow up to 4GB when muli-page bvec is enabled.
> > > > > > > > but sometimes it would lead to inefficient behaviors.
> > > > > > > > in case of large chunk direct I/O, - 32MB chunk read in user
> > > > > > > > space -
> > > > > > > > all pages for 32MB would be merged to a bio structure if the
> > > > > > > > pages
> > > > > > > > physical addresses are contiguous. it makes some delay to submit
> > > > > > > > until merge complete. bio max size should be limited to a
> > > > > > > > proper size.
> > > > > > > >
> > > > > > > > When 32MB chunk read with direct I/O option is coming from
> > > > > > > > userspace,
> > > > > > > > kernel behavior is below now in do_direct_IO() loop. it's
> > > > > > > > timeline.
> > > > > > > >
> > > > > > > > | bio merge for 32MB. total 8,192 pages are merged.
> > > > > > > > | total elapsed time is over 2ms.
> > > > > > > > |-- ... --->|
> > > > > > > > | 8,192 pages
> > > > > > > > merged a bio.
> > > > > > > > | at this
> > > > > > > > time, first bio submit is done.
> > > > > > > > | 1 bio is
> > > > > > > > split to 32 read request and issue.
> > > > > > > >
> > > > > > > > |--->
> > > > > > > >
> > > > > > > > |--->
> > > > > > > >
> > > > > > > > |--->
> > > > > > > >
> > > > > > > > ..
> > > > > > > >
> > > > > > > >|--->
> > > > > > > >
> > > > > > > > |--->|
> > > > > > > > total 19ms elapsed to complete 32MB
> > > > > > > > read done from device. |
> > > > > > > >
> > > > > > > > If bio max size is limited with 1MB, behavior is changed below.
> > > > > > > >
> > > > > > > > | bio merge for 1MB. 256 pages are merged for each bio.
> > > > > > > > | total 32 bio will be made.
> > > > > > > > | total elapsed time is over 2ms. it's same.
> > > > > > > > | but, first bio submit timing is fast. about 100us.
> > > > > > > > |--->|--->|--->|---> ... -->|--->|--->|--->|--->|
> > > > > > > > | 256 pages merged a bio.
> > > > > > > > | at this time, first bio submit is done.
> > > > > > > > | and 1 read request is issued for 1 bio.
> > > > > > > > |--->
> > > > > > > >|--->
> > > > > > > > |--->
> > > > > > > > ..
> > > > > > > >
> > > > > > > > |--->
> > > > > > > >
> > > > > > > > |--->|
> > > > > > > > total 17ms elapsed to complete 32MB read done from
> > > > > > > > device. |
> > > > > > > >
> > > > > > > > As a result, read request issue timing is faster if bio max
> > > > > > > > size is limited.
> > > > > > > > Current kernel behavior with multipage bvec, super large bio
> > > > > > > > can be created.
> > > > > > > > And it lead to delay first I/O request issue.
> > > > > > > >
> > > > > > > > Signed-off-by: Changheun Lee
> > > > > > > > ---
> > > > > > > > block/bio.c| 13 -
> > > > > > > > include/linux/bio.h| 2 +-
> > > > > > > > include/linux/blkdev.h | 3 +++
> > > > > > > > 3 files changed, 16 insertions(+), 2 deletions(-)
> > > > > > > >
> > > > > > > > diff --git a/block/bio.c b/block/bio.c
> > > > > > > > index 1f2cc1fbe283..c528e1f944c7 100644
> > > > > > > > --- a/block/bio.c
> > > > > > > > +++ b/block/bio.c
> > > > > > > > @@ -287,6 +287,17 @@ void bio_init(struct bio *bio, struct
> > > > > > > > bio_vec *table,
> > > > > > > > }
> > > > > > > > EXPORT_SYMBOL(bio_init);
> > > > > > > >
> > > > > > > > +unsigned int bio_max_size(struct bio *bio)
> > > > > > > > +{
> > > > > > > > + struct request_queue *q = bio->bi_disk->queue;
> > > > > > > > +
> > > > > > > > + if (blk_queue_limit_bio_size(q))
> > > > > > > > + return blk_queue_get_max_sectors(q, bio_op(bio))
> > > > > > > > + << SECTOR_SHIFT;
> > > > > > > > +
> > > > > > > > + return UINT_MAX;
> > > > > > > > +}
> > > > > > > > +
> > > > > > > > /**
> > > > > > > > * bio_reset - reinitialize a bio
> > > > > >
Re: [RESEND PATCH v5 1/2] bio: limit bio max size
> On Wed, Apr 07, 2021 at 02:06:33PM +0900, Changheun Lee wrote:
> > > On Wed, Apr 07, 2021 at 09:16:12AM +0900, Changheun Lee wrote:
> > > > > On Tue, Apr 06, 2021 at 10:31:28AM +0900, Changheun Lee wrote:
> > > > > > > bio size can grow up to 4GB when muli-page bvec is enabled.
> > > > > > > but sometimes it would lead to inefficient behaviors.
> > > > > > > in case of large chunk direct I/O, - 32MB chunk read in user
> > > > > > > space -
> > > > > > > all pages for 32MB would be merged to a bio structure if the pages
> > > > > > > physical addresses are contiguous. it makes some delay to submit
> > > > > > > until merge complete. bio max size should be limited to a proper
> > > > > > > size.
> > > > > > >
> > > > > > > When 32MB chunk read with direct I/O option is coming from
> > > > > > > userspace,
> > > > > > > kernel behavior is below now in do_direct_IO() loop. it's
> > > > > > > timeline.
> > > > > > >
> > > > > > > | bio merge for 32MB. total 8,192 pages are merged.
> > > > > > > | total elapsed time is over 2ms.
> > > > > > > |-- ... --->|
> > > > > > > | 8,192 pages
> > > > > > > merged a bio.
> > > > > > > | at this time,
> > > > > > > first bio submit is done.
> > > > > > > | 1 bio is split
> > > > > > > to 32 read request and issue.
> > > > > > > |--->
> > > > > > >
> > > > > > > |--->
> > > > > > >
> > > > > > > |--->
> > > > > > >
> > > > > > > ..
> > > > > > >
> > > > > > > |--->
> > > > > > >
> > > > > > > |--->|
> > > > > > > total 19ms elapsed to complete 32MB
> > > > > > > read done from device. |
> > > > > > >
> > > > > > > If bio max size is limited with 1MB, behavior is changed below.
> > > > > > >
> > > > > > > | bio merge for 1MB. 256 pages are merged for each bio.
> > > > > > > | total 32 bio will be made.
> > > > > > > | total elapsed time is over 2ms. it's same.
> > > > > > > | but, first bio submit timing is fast. about 100us.
> > > > > > > |--->|--->|--->|---> ... -->|--->|--->|--->|--->|
> > > > > > > | 256 pages merged a bio.
> > > > > > > | at this time, first bio submit is done.
> > > > > > > | and 1 read request is issued for 1 bio.
> > > > > > > |--->
> > > > > > >|--->
> > > > > > > |--->
> > > > > > > ..
> > > > > > > |--->
> > > > > > >
> > > > > > > |--->|
> > > > > > > total 17ms elapsed to complete 32MB read done from
> > > > > > > device. |
> > > > > > >
> > > > > > > As a result, read request issue timing is faster if bio max size
> > > > > > > is limited.
> > > > > > > Current kernel behavior with multipage bvec, super large bio can
> > > > > > > be created.
> > > > > > > And it lead to delay first I/O request issue.
> > > > > > >
> > > > > > > Signed-off-by: Changheun Lee
> > > > > > > ---
> > > > > > > block/bio.c| 13 -
> > > > > > > include/linux/bio.h| 2 +-
> > > > > > > include/linux/blkdev.h | 3 +++
> > > > > > > 3 files changed, 16 insertions(+), 2 deletions(-)
> > > > > > >
> > > > > > > diff --git a/block/bio.c b/block/bio.c
> > > > > > > index 1f2cc1fbe283..c528e1f944c7 100644
> > > > > > > --- a/block/bio.c
> > > > > > > +++ b/block/bio.c
> > > > > > > @@ -287,6 +287,17 @@ void bio_init(struct bio *bio, struct
> > > > > > > bio_vec *table,
> > > > > > > }
> > > > > > > EXPORT_SYMBOL(bio_init);
> > > > > > >
> > > > > > > +unsigned int bio_max_size(struct bio *bio)
> > > > > > > +{
> > > > > > > + struct request_queue *q = bio->bi_disk->queue;
> > > > > > > +
> > > > > > > + if (blk_queue_limit_bio_size(q))
> > > > > > > + return blk_queue_get_max_sectors(q, bio_op(bio))
> > > > > > > + << SECTOR_SHIFT;
> > > > > > > +
> > > > > > > + return UINT_MAX;
> > > > > > > +}
> > > > > > > +
> > > > > > > /**
> > > > > > > * bio_reset - reinitialize a bio
> > > > > > > * @bio: bio to reset
> > > > > > > @@ -877,7 +888,7 @@ bool __bio_try_merge_page(struct bio *bio,
> > > > > > > struct page *page,
> > > > > > > struct bio_vec *bv = >bi_io_vec[bio->bi_vcnt - 1];
> > > > > > >
> > > > > > > if (page_is_mergeable(bv, page, len, off, same_page)) {
> > > > > > > -
Re: [RESEND PATCH v5 1/2] bio: limit bio max size
On Wed, Apr 07, 2021 at 02:06:33PM +0900, Changheun Lee wrote:
> > On Wed, Apr 07, 2021 at 09:16:12AM +0900, Changheun Lee wrote:
> > > > On Tue, Apr 06, 2021 at 10:31:28AM +0900, Changheun Lee wrote:
> > > > > > bio size can grow up to 4GB when muli-page bvec is enabled.
> > > > > > but sometimes it would lead to inefficient behaviors.
> > > > > > in case of large chunk direct I/O, - 32MB chunk read in user space -
> > > > > > all pages for 32MB would be merged to a bio structure if the pages
> > > > > > physical addresses are contiguous. it makes some delay to submit
> > > > > > until merge complete. bio max size should be limited to a proper
> > > > > > size.
> > > > > >
> > > > > > When 32MB chunk read with direct I/O option is coming from
> > > > > > userspace,
> > > > > > kernel behavior is below now in do_direct_IO() loop. it's timeline.
> > > > > >
> > > > > > | bio merge for 32MB. total 8,192 pages are merged.
> > > > > > | total elapsed time is over 2ms.
> > > > > > |-- ... --->|
> > > > > > | 8,192 pages
> > > > > > merged a bio.
> > > > > > | at this time,
> > > > > > first bio submit is done.
> > > > > > | 1 bio is split
> > > > > > to 32 read request and issue.
> > > > > > |--->
> > > > > > |--->
> > > > > >|--->
> > > > > > ..
> > > > > >
> > > > > > |--->
> > > > > >
> > > > > > |--->|
> > > > > > total 19ms elapsed to complete 32MB read
> > > > > > done from device. |
> > > > > >
> > > > > > If bio max size is limited with 1MB, behavior is changed below.
> > > > > >
> > > > > > | bio merge for 1MB. 256 pages are merged for each bio.
> > > > > > | total 32 bio will be made.
> > > > > > | total elapsed time is over 2ms. it's same.
> > > > > > | but, first bio submit timing is fast. about 100us.
> > > > > > |--->|--->|--->|---> ... -->|--->|--->|--->|--->|
> > > > > > | 256 pages merged a bio.
> > > > > > | at this time, first bio submit is done.
> > > > > > | and 1 read request is issued for 1 bio.
> > > > > > |--->
> > > > > >|--->
> > > > > > |--->
> > > > > > ..
> > > > > > |--->
> > > > > > |--->|
> > > > > > total 17ms elapsed to complete 32MB read done from device. |
> > > > > >
> > > > > > As a result, read request issue timing is faster if bio max size is
> > > > > > limited.
> > > > > > Current kernel behavior with multipage bvec, super large bio can be
> > > > > > created.
> > > > > > And it lead to delay first I/O request issue.
> > > > > >
> > > > > > Signed-off-by: Changheun Lee
> > > > > > ---
> > > > > > block/bio.c| 13 -
> > > > > > include/linux/bio.h| 2 +-
> > > > > > include/linux/blkdev.h | 3 +++
> > > > > > 3 files changed, 16 insertions(+), 2 deletions(-)
> > > > > >
> > > > > > diff --git a/block/bio.c b/block/bio.c
> > > > > > index 1f2cc1fbe283..c528e1f944c7 100644
> > > > > > --- a/block/bio.c
> > > > > > +++ b/block/bio.c
> > > > > > @@ -287,6 +287,17 @@ void bio_init(struct bio *bio, struct bio_vec
> > > > > > *table,
> > > > > > }
> > > > > > EXPORT_SYMBOL(bio_init);
> > > > > >
> > > > > > +unsigned int bio_max_size(struct bio *bio)
> > > > > > +{
> > > > > > + struct request_queue *q = bio->bi_disk->queue;
> > > > > > +
> > > > > > + if (blk_queue_limit_bio_size(q))
> > > > > > + return blk_queue_get_max_sectors(q, bio_op(bio))
> > > > > > + << SECTOR_SHIFT;
> > > > > > +
> > > > > > + return UINT_MAX;
> > > > > > +}
> > > > > > +
> > > > > > /**
> > > > > > * bio_reset - reinitialize a bio
> > > > > > * @bio: bio to reset
> > > > > > @@ -877,7 +888,7 @@ bool __bio_try_merge_page(struct bio *bio,
> > > > > > struct page *page,
> > > > > > struct bio_vec *bv = >bi_io_vec[bio->bi_vcnt - 1];
> > > > > >
> > > > > > if (page_is_mergeable(bv, page, len, off, same_page)) {
> > > > > > - if (bio->bi_iter.bi_size > UINT_MAX - len) {
> > > > > > + if (bio->bi_iter.bi_size > bio_max_size(bio) -
> > > > > > len) {
> > > > > > *same_page = false;
> > > > > > return false;
> > > > > >
Re: [RESEND PATCH v5 1/2] bio: limit bio max size
> On Wed, Apr 07, 2021 at 09:16:12AM +0900, Changheun Lee wrote:
> > > On Tue, Apr 06, 2021 at 10:31:28AM +0900, Changheun Lee wrote:
> > > > > bio size can grow up to 4GB when muli-page bvec is enabled.
> > > > > but sometimes it would lead to inefficient behaviors.
> > > > > in case of large chunk direct I/O, - 32MB chunk read in user space -
> > > > > all pages for 32MB would be merged to a bio structure if the pages
> > > > > physical addresses are contiguous. it makes some delay to submit
> > > > > until merge complete. bio max size should be limited to a proper size.
> > > > >
> > > > > When 32MB chunk read with direct I/O option is coming from userspace,
> > > > > kernel behavior is below now in do_direct_IO() loop. it's timeline.
> > > > >
> > > > > | bio merge for 32MB. total 8,192 pages are merged.
> > > > > | total elapsed time is over 2ms.
> > > > > |-- ... --->|
> > > > > | 8,192 pages merged
> > > > > a bio.
> > > > > | at this time,
> > > > > first bio submit is done.
> > > > > | 1 bio is split to
> > > > > 32 read request and issue.
> > > > > |--->
> > > > > |--->
> > > > >|--->
> > > > > ..
> > > > >
> > > > > |--->
> > > > >
> > > > > |--->|
> > > > > total 19ms elapsed to complete 32MB read
> > > > > done from device. |
> > > > >
> > > > > If bio max size is limited with 1MB, behavior is changed below.
> > > > >
> > > > > | bio merge for 1MB. 256 pages are merged for each bio.
> > > > > | total 32 bio will be made.
> > > > > | total elapsed time is over 2ms. it's same.
> > > > > | but, first bio submit timing is fast. about 100us.
> > > > > |--->|--->|--->|---> ... -->|--->|--->|--->|--->|
> > > > > | 256 pages merged a bio.
> > > > > | at this time, first bio submit is done.
> > > > > | and 1 read request is issued for 1 bio.
> > > > > |--->
> > > > >|--->
> > > > > |--->
> > > > > ..
> > > > > |--->
> > > > > |--->|
> > > > > total 17ms elapsed to complete 32MB read done from device. |
> > > > >
> > > > > As a result, read request issue timing is faster if bio max size is
> > > > > limited.
> > > > > Current kernel behavior with multipage bvec, super large bio can be
> > > > > created.
> > > > > And it lead to delay first I/O request issue.
> > > > >
> > > > > Signed-off-by: Changheun Lee
> > > > > ---
> > > > > block/bio.c| 13 -
> > > > > include/linux/bio.h| 2 +-
> > > > > include/linux/blkdev.h | 3 +++
> > > > > 3 files changed, 16 insertions(+), 2 deletions(-)
> > > > >
> > > > > diff --git a/block/bio.c b/block/bio.c
> > > > > index 1f2cc1fbe283..c528e1f944c7 100644
> > > > > --- a/block/bio.c
> > > > > +++ b/block/bio.c
> > > > > @@ -287,6 +287,17 @@ void bio_init(struct bio *bio, struct bio_vec
> > > > > *table,
> > > > > }
> > > > > EXPORT_SYMBOL(bio_init);
> > > > >
> > > > > +unsigned int bio_max_size(struct bio *bio)
> > > > > +{
> > > > > + struct request_queue *q = bio->bi_disk->queue;
> > > > > +
> > > > > + if (blk_queue_limit_bio_size(q))
> > > > > + return blk_queue_get_max_sectors(q, bio_op(bio))
> > > > > + << SECTOR_SHIFT;
> > > > > +
> > > > > + return UINT_MAX;
> > > > > +}
> > > > > +
> > > > > /**
> > > > > * bio_reset - reinitialize a bio
> > > > > * @bio: bio to reset
> > > > > @@ -877,7 +888,7 @@ bool __bio_try_merge_page(struct bio *bio, struct
> > > > > page *page,
> > > > > struct bio_vec *bv = >bi_io_vec[bio->bi_vcnt - 1];
> > > > >
> > > > > if (page_is_mergeable(bv, page, len, off, same_page)) {
> > > > > - if (bio->bi_iter.bi_size > UINT_MAX - len) {
> > > > > + if (bio->bi_iter.bi_size > bio_max_size(bio) -
> > > > > len) {
> > > > > *same_page = false;
> > > > > return false;
> > > > > }
> > > > > diff --git a/include/linux/bio.h b/include/linux/bio.h
> > > > > index 1edda614f7ce..13b6f6562a5b 100644
> > > > > --- a/include/linux/bio.h
> > > > > +++ b/include/linux/bio.h
> > > > > @@ -113,7 +113,7 @@ static inline bool
Re: [RESEND PATCH v5 1/2] bio: limit bio max size
On Wed, Apr 07, 2021 at 09:16:12AM +0900, Changheun Lee wrote:
> > On Tue, Apr 06, 2021 at 10:31:28AM +0900, Changheun Lee wrote:
> > > > bio size can grow up to 4GB when muli-page bvec is enabled.
> > > > but sometimes it would lead to inefficient behaviors.
> > > > in case of large chunk direct I/O, - 32MB chunk read in user space -
> > > > all pages for 32MB would be merged to a bio structure if the pages
> > > > physical addresses are contiguous. it makes some delay to submit
> > > > until merge complete. bio max size should be limited to a proper size.
> > > >
> > > > When 32MB chunk read with direct I/O option is coming from userspace,
> > > > kernel behavior is below now in do_direct_IO() loop. it's timeline.
> > > >
> > > > | bio merge for 32MB. total 8,192 pages are merged.
> > > > | total elapsed time is over 2ms.
> > > > |-- ... --->|
> > > > | 8,192 pages merged a
> > > > bio.
> > > > | at this time, first
> > > > bio submit is done.
> > > > | 1 bio is split to 32
> > > > read request and issue.
> > > > |--->
> > > > |--->
> > > >|--->
> > > > ..
> > > >
> > > > |--->
> > > >
> > > > |--->|
> > > > total 19ms elapsed to complete 32MB read done
> > > > from device. |
> > > >
> > > > If bio max size is limited with 1MB, behavior is changed below.
> > > >
> > > > | bio merge for 1MB. 256 pages are merged for each bio.
> > > > | total 32 bio will be made.
> > > > | total elapsed time is over 2ms. it's same.
> > > > | but, first bio submit timing is fast. about 100us.
> > > > |--->|--->|--->|---> ... -->|--->|--->|--->|--->|
> > > > | 256 pages merged a bio.
> > > > | at this time, first bio submit is done.
> > > > | and 1 read request is issued for 1 bio.
> > > > |--->
> > > >|--->
> > > > |--->
> > > > ..
> > > > |--->
> > > > |--->|
> > > > total 17ms elapsed to complete 32MB read done from device. |
> > > >
> > > > As a result, read request issue timing is faster if bio max size is
> > > > limited.
> > > > Current kernel behavior with multipage bvec, super large bio can be
> > > > created.
> > > > And it lead to delay first I/O request issue.
> > > >
> > > > Signed-off-by: Changheun Lee
> > > > ---
> > > > block/bio.c| 13 -
> > > > include/linux/bio.h| 2 +-
> > > > include/linux/blkdev.h | 3 +++
> > > > 3 files changed, 16 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/block/bio.c b/block/bio.c
> > > > index 1f2cc1fbe283..c528e1f944c7 100644
> > > > --- a/block/bio.c
> > > > +++ b/block/bio.c
> > > > @@ -287,6 +287,17 @@ void bio_init(struct bio *bio, struct bio_vec
> > > > *table,
> > > > }
> > > > EXPORT_SYMBOL(bio_init);
> > > >
> > > > +unsigned int bio_max_size(struct bio *bio)
> > > > +{
> > > > + struct request_queue *q = bio->bi_disk->queue;
> > > > +
> > > > + if (blk_queue_limit_bio_size(q))
> > > > + return blk_queue_get_max_sectors(q, bio_op(bio))
> > > > + << SECTOR_SHIFT;
> > > > +
> > > > + return UINT_MAX;
> > > > +}
> > > > +
> > > > /**
> > > > * bio_reset - reinitialize a bio
> > > > * @bio: bio to reset
> > > > @@ -877,7 +888,7 @@ bool __bio_try_merge_page(struct bio *bio, struct
> > > > page *page,
> > > > struct bio_vec *bv = >bi_io_vec[bio->bi_vcnt - 1];
> > > >
> > > > if (page_is_mergeable(bv, page, len, off, same_page)) {
> > > > - if (bio->bi_iter.bi_size > UINT_MAX - len) {
> > > > + if (bio->bi_iter.bi_size > bio_max_size(bio) -
> > > > len) {
> > > > *same_page = false;
> > > > return false;
> > > > }
> > > > diff --git a/include/linux/bio.h b/include/linux/bio.h
> > > > index 1edda614f7ce..13b6f6562a5b 100644
> > > > --- a/include/linux/bio.h
> > > > +++ b/include/linux/bio.h
> > > > @@ -113,7 +113,7 @@ static inline bool bio_full(struct bio *bio,
> > > > unsigned len)
> > > > if (bio->bi_vcnt >= bio->bi_max_vecs)
> > > > return true;
> > > >
> > > > - if
Re: [RESEND PATCH v5 1/2] bio: limit bio max size
> On Tue, Apr 06, 2021 at 10:31:28AM +0900, Changheun Lee wrote:
> > > bio size can grow up to 4GB when muli-page bvec is enabled.
> > > but sometimes it would lead to inefficient behaviors.
> > > in case of large chunk direct I/O, - 32MB chunk read in user space -
> > > all pages for 32MB would be merged to a bio structure if the pages
> > > physical addresses are contiguous. it makes some delay to submit
> > > until merge complete. bio max size should be limited to a proper size.
> > >
> > > When 32MB chunk read with direct I/O option is coming from userspace,
> > > kernel behavior is below now in do_direct_IO() loop. it's timeline.
> > >
> > > | bio merge for 32MB. total 8,192 pages are merged.
> > > | total elapsed time is over 2ms.
> > > |-- ... --->|
> > > | 8,192 pages merged a
> > > bio.
> > > | at this time, first
> > > bio submit is done.
> > > | 1 bio is split to 32
> > > read request and issue.
> > > |--->
> > > |--->
> > >|--->
> > > ..
> > >
> > > |--->
> > >
> > > |--->|
> > > total 19ms elapsed to complete 32MB read done
> > > from device. |
> > >
> > > If bio max size is limited with 1MB, behavior is changed below.
> > >
> > > | bio merge for 1MB. 256 pages are merged for each bio.
> > > | total 32 bio will be made.
> > > | total elapsed time is over 2ms. it's same.
> > > | but, first bio submit timing is fast. about 100us.
> > > |--->|--->|--->|---> ... -->|--->|--->|--->|--->|
> > > | 256 pages merged a bio.
> > > | at this time, first bio submit is done.
> > > | and 1 read request is issued for 1 bio.
> > > |--->
> > >|--->
> > > |--->
> > > ..
> > > |--->
> > > |--->|
> > > total 17ms elapsed to complete 32MB read done from device. |
> > >
> > > As a result, read request issue timing is faster if bio max size is
> > > limited.
> > > Current kernel behavior with multipage bvec, super large bio can be
> > > created.
> > > And it lead to delay first I/O request issue.
> > >
> > > Signed-off-by: Changheun Lee
> > > ---
> > > block/bio.c| 13 -
> > > include/linux/bio.h| 2 +-
> > > include/linux/blkdev.h | 3 +++
> > > 3 files changed, 16 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/block/bio.c b/block/bio.c
> > > index 1f2cc1fbe283..c528e1f944c7 100644
> > > --- a/block/bio.c
> > > +++ b/block/bio.c
> > > @@ -287,6 +287,17 @@ void bio_init(struct bio *bio, struct bio_vec *table,
> > > }
> > > EXPORT_SYMBOL(bio_init);
> > >
> > > +unsigned int bio_max_size(struct bio *bio)
> > > +{
> > > + struct request_queue *q = bio->bi_disk->queue;
> > > +
> > > + if (blk_queue_limit_bio_size(q))
> > > + return blk_queue_get_max_sectors(q, bio_op(bio))
> > > + << SECTOR_SHIFT;
> > > +
> > > + return UINT_MAX;
> > > +}
> > > +
> > > /**
> > > * bio_reset - reinitialize a bio
> > > * @bio: bio to reset
> > > @@ -877,7 +888,7 @@ bool __bio_try_merge_page(struct bio *bio, struct
> > > page *page,
> > > struct bio_vec *bv = >bi_io_vec[bio->bi_vcnt - 1];
> > >
> > > if (page_is_mergeable(bv, page, len, off, same_page)) {
> > > - if (bio->bi_iter.bi_size > UINT_MAX - len) {
> > > + if (bio->bi_iter.bi_size > bio_max_size(bio) - len) {
> > > *same_page = false;
> > > return false;
> > > }
> > > diff --git a/include/linux/bio.h b/include/linux/bio.h
> > > index 1edda614f7ce..13b6f6562a5b 100644
> > > --- a/include/linux/bio.h
> > > +++ b/include/linux/bio.h
> > > @@ -113,7 +113,7 @@ static inline bool bio_full(struct bio *bio, unsigned
> > > len)
> > > if (bio->bi_vcnt >= bio->bi_max_vecs)
> > > return true;
> > >
> > > - if (bio->bi_iter.bi_size > UINT_MAX - len)
> > > + if (bio->bi_iter.bi_size > bio_max_size(bio) - len)
> > > return true;
> > >
> > > return false;
> > > diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> > > index f94ee3089e01..3aeab9e7e97b 100644
> > > --- a/include/linux/blkdev.h
> > > +++ b/include/linux/blkdev.h
> > > @@ -621,6 +621,7 @@ struct request_queue {
> >
Re: [RESEND PATCH v5 1/2] bio: limit bio max size
On Tue, Apr 06, 2021 at 10:31:28AM +0900, Changheun Lee wrote:
> > bio size can grow up to 4GB when muli-page bvec is enabled.
> > but sometimes it would lead to inefficient behaviors.
> > in case of large chunk direct I/O, - 32MB chunk read in user space -
> > all pages for 32MB would be merged to a bio structure if the pages
> > physical addresses are contiguous. it makes some delay to submit
> > until merge complete. bio max size should be limited to a proper size.
> >
> > When 32MB chunk read with direct I/O option is coming from userspace,
> > kernel behavior is below now in do_direct_IO() loop. it's timeline.
> >
> > | bio merge for 32MB. total 8,192 pages are merged.
> > | total elapsed time is over 2ms.
> > |-- ... --->|
> > | 8,192 pages merged a bio.
> > | at this time, first bio
> > submit is done.
> > | 1 bio is split to 32
> > read request and issue.
> > |--->
> > |--->
> >|--->
> > ..
> >
> > |--->
> >
> > |--->|
> > total 19ms elapsed to complete 32MB read done
> > from device. |
> >
> > If bio max size is limited with 1MB, behavior is changed below.
> >
> > | bio merge for 1MB. 256 pages are merged for each bio.
> > | total 32 bio will be made.
> > | total elapsed time is over 2ms. it's same.
> > | but, first bio submit timing is fast. about 100us.
> > |--->|--->|--->|---> ... -->|--->|--->|--->|--->|
> > | 256 pages merged a bio.
> > | at this time, first bio submit is done.
> > | and 1 read request is issued for 1 bio.
> > |--->
> >|--->
> > |--->
> > ..
> > |--->
> > |--->|
> > total 17ms elapsed to complete 32MB read done from device. |
> >
> > As a result, read request issue timing is faster if bio max size is limited.
> > Current kernel behavior with multipage bvec, super large bio can be created.
> > And it lead to delay first I/O request issue.
> >
> > Signed-off-by: Changheun Lee
> > ---
> > block/bio.c| 13 -
> > include/linux/bio.h| 2 +-
> > include/linux/blkdev.h | 3 +++
> > 3 files changed, 16 insertions(+), 2 deletions(-)
> >
> > diff --git a/block/bio.c b/block/bio.c
> > index 1f2cc1fbe283..c528e1f944c7 100644
> > --- a/block/bio.c
> > +++ b/block/bio.c
> > @@ -287,6 +287,17 @@ void bio_init(struct bio *bio, struct bio_vec *table,
> > }
> > EXPORT_SYMBOL(bio_init);
> >
> > +unsigned int bio_max_size(struct bio *bio)
> > +{
> > + struct request_queue *q = bio->bi_disk->queue;
> > +
> > + if (blk_queue_limit_bio_size(q))
> > + return blk_queue_get_max_sectors(q, bio_op(bio))
> > + << SECTOR_SHIFT;
> > +
> > + return UINT_MAX;
> > +}
> > +
> > /**
> > * bio_reset - reinitialize a bio
> > * @bio: bio to reset
> > @@ -877,7 +888,7 @@ bool __bio_try_merge_page(struct bio *bio, struct page
> > *page,
> > struct bio_vec *bv = >bi_io_vec[bio->bi_vcnt - 1];
> >
> > if (page_is_mergeable(bv, page, len, off, same_page)) {
> > - if (bio->bi_iter.bi_size > UINT_MAX - len) {
> > + if (bio->bi_iter.bi_size > bio_max_size(bio) - len) {
> > *same_page = false;
> > return false;
> > }
> > diff --git a/include/linux/bio.h b/include/linux/bio.h
> > index 1edda614f7ce..13b6f6562a5b 100644
> > --- a/include/linux/bio.h
> > +++ b/include/linux/bio.h
> > @@ -113,7 +113,7 @@ static inline bool bio_full(struct bio *bio, unsigned
> > len)
> > if (bio->bi_vcnt >= bio->bi_max_vecs)
> > return true;
> >
> > - if (bio->bi_iter.bi_size > UINT_MAX - len)
> > + if (bio->bi_iter.bi_size > bio_max_size(bio) - len)
> > return true;
> >
> > return false;
> > diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> > index f94ee3089e01..3aeab9e7e97b 100644
> > --- a/include/linux/blkdev.h
> > +++ b/include/linux/blkdev.h
> > @@ -621,6 +621,7 @@ struct request_queue {
> > #define QUEUE_FLAG_RQ_ALLOC_TIME 27/* record rq->alloc_time_ns */
> > #define QUEUE_FLAG_HCTX_ACTIVE 28 /* at least one blk-mq hctx is
> > active */
> > #define QUEUE_FLAG_NOWAIT
[RESEND PATCH v5 1/2] bio: limit bio max size
> bio size can grow up to 4GB when muli-page bvec is enabled.
> but sometimes it would lead to inefficient behaviors.
> in case of large chunk direct I/O, - 32MB chunk read in user space -
> all pages for 32MB would be merged to a bio structure if the pages
> physical addresses are contiguous. it makes some delay to submit
> until merge complete. bio max size should be limited to a proper size.
>
> When 32MB chunk read with direct I/O option is coming from userspace,
> kernel behavior is below now in do_direct_IO() loop. it's timeline.
>
> | bio merge for 32MB. total 8,192 pages are merged.
> | total elapsed time is over 2ms.
> |-- ... --->|
> | 8,192 pages merged a bio.
> | at this time, first bio
> submit is done.
> | 1 bio is split to 32 read
> request and issue.
> |--->
> |--->
>|--->
> ..
>
> |--->
>
> |--->|
> total 19ms elapsed to complete 32MB read done from
> device. |
>
> If bio max size is limited with 1MB, behavior is changed below.
>
> | bio merge for 1MB. 256 pages are merged for each bio.
> | total 32 bio will be made.
> | total elapsed time is over 2ms. it's same.
> | but, first bio submit timing is fast. about 100us.
> |--->|--->|--->|---> ... -->|--->|--->|--->|--->|
> | 256 pages merged a bio.
> | at this time, first bio submit is done.
> | and 1 read request is issued for 1 bio.
> |--->
>|--->
> |--->
> ..
> |--->
> |--->|
> total 17ms elapsed to complete 32MB read done from device. |
>
> As a result, read request issue timing is faster if bio max size is limited.
> Current kernel behavior with multipage bvec, super large bio can be created.
> And it lead to delay first I/O request issue.
>
> Signed-off-by: Changheun Lee
> ---
> block/bio.c| 13 -
> include/linux/bio.h| 2 +-
> include/linux/blkdev.h | 3 +++
> 3 files changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/block/bio.c b/block/bio.c
> index 1f2cc1fbe283..c528e1f944c7 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -287,6 +287,17 @@ void bio_init(struct bio *bio, struct bio_vec *table,
> }
> EXPORT_SYMBOL(bio_init);
>
> +unsigned int bio_max_size(struct bio *bio)
> +{
> + struct request_queue *q = bio->bi_disk->queue;
> +
> + if (blk_queue_limit_bio_size(q))
> + return blk_queue_get_max_sectors(q, bio_op(bio))
> + << SECTOR_SHIFT;
> +
> + return UINT_MAX;
> +}
> +
> /**
> * bio_reset - reinitialize a bio
> * @bio: bio to reset
> @@ -877,7 +888,7 @@ bool __bio_try_merge_page(struct bio *bio, struct page
> *page,
> struct bio_vec *bv = >bi_io_vec[bio->bi_vcnt - 1];
>
> if (page_is_mergeable(bv, page, len, off, same_page)) {
> - if (bio->bi_iter.bi_size > UINT_MAX - len) {
> + if (bio->bi_iter.bi_size > bio_max_size(bio) - len) {
> *same_page = false;
> return false;
> }
> diff --git a/include/linux/bio.h b/include/linux/bio.h
> index 1edda614f7ce..13b6f6562a5b 100644
> --- a/include/linux/bio.h
> +++ b/include/linux/bio.h
> @@ -113,7 +113,7 @@ static inline bool bio_full(struct bio *bio, unsigned len)
> if (bio->bi_vcnt >= bio->bi_max_vecs)
> return true;
>
> - if (bio->bi_iter.bi_size > UINT_MAX - len)
> + if (bio->bi_iter.bi_size > bio_max_size(bio) - len)
> return true;
>
> return false;
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index f94ee3089e01..3aeab9e7e97b 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -621,6 +621,7 @@ struct request_queue {
> #define QUEUE_FLAG_RQ_ALLOC_TIME 27 /* record rq->alloc_time_ns */
> #define QUEUE_FLAG_HCTX_ACTIVE 28 /* at least one blk-mq hctx is
> active */
> #define QUEUE_FLAG_NOWAIT 29 /* device supports NOWAIT */
> +#define QUEUE_FLAG_LIMIT_BIO_SIZE 30 /* limit bio size */
>
> #define QUEUE_FLAG_MQ_DEFAULT((1 << QUEUE_FLAG_IO_STAT) |
> \
>(1 << QUEUE_FLAG_SAME_COMP) |
[RESEND PATCH v5 1/2] bio: limit bio max size
bio size can grow up to 4GB when muli-page bvec is enabled.
but sometimes it would lead to inefficient behaviors.
in case of large chunk direct I/O, - 32MB chunk read in user space -
all pages for 32MB would be merged to a bio structure if the pages
physical addresses are contiguous. it makes some delay to submit
until merge complete. bio max size should be limited to a proper size.
When 32MB chunk read with direct I/O option is coming from userspace,
kernel behavior is below now in do_direct_IO() loop. it's timeline.
| bio merge for 32MB. total 8,192 pages are merged.
| total elapsed time is over 2ms.
|-- ... --->|
| 8,192 pages merged a bio.
| at this time, first bio
submit is done.
| 1 bio is split to 32 read
request and issue.
|--->
|--->
|--->
..
|--->
|--->|
total 19ms elapsed to complete 32MB read done from
device. |
If bio max size is limited with 1MB, behavior is changed below.
| bio merge for 1MB. 256 pages are merged for each bio.
| total 32 bio will be made.
| total elapsed time is over 2ms. it's same.
| but, first bio submit timing is fast. about 100us.
|--->|--->|--->|---> ... -->|--->|--->|--->|--->|
| 256 pages merged a bio.
| at this time, first bio submit is done.
| and 1 read request is issued for 1 bio.
|--->
|--->
|--->
..
|--->
|--->|
total 17ms elapsed to complete 32MB read done from device. |
As a result, read request issue timing is faster if bio max size is limited.
Current kernel behavior with multipage bvec, super large bio can be created.
And it lead to delay first I/O request issue.
Signed-off-by: Changheun Lee
---
block/bio.c| 13 -
include/linux/bio.h| 2 +-
include/linux/blkdev.h | 3 +++
3 files changed, 16 insertions(+), 2 deletions(-)
diff --git a/block/bio.c b/block/bio.c
index 1f2cc1fbe283..c528e1f944c7 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -287,6 +287,17 @@ void bio_init(struct bio *bio, struct bio_vec *table,
}
EXPORT_SYMBOL(bio_init);
+unsigned int bio_max_size(struct bio *bio)
+{
+ struct request_queue *q = bio->bi_disk->queue;
+
+ if (blk_queue_limit_bio_size(q))
+ return blk_queue_get_max_sectors(q, bio_op(bio))
+ << SECTOR_SHIFT;
+
+ return UINT_MAX;
+}
+
/**
* bio_reset - reinitialize a bio
* @bio: bio to reset
@@ -877,7 +888,7 @@ bool __bio_try_merge_page(struct bio *bio, struct page
*page,
struct bio_vec *bv = >bi_io_vec[bio->bi_vcnt - 1];
if (page_is_mergeable(bv, page, len, off, same_page)) {
- if (bio->bi_iter.bi_size > UINT_MAX - len) {
+ if (bio->bi_iter.bi_size > bio_max_size(bio) - len) {
*same_page = false;
return false;
}
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 1edda614f7ce..13b6f6562a5b 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -113,7 +113,7 @@ static inline bool bio_full(struct bio *bio, unsigned len)
if (bio->bi_vcnt >= bio->bi_max_vecs)
return true;
- if (bio->bi_iter.bi_size > UINT_MAX - len)
+ if (bio->bi_iter.bi_size > bio_max_size(bio) - len)
return true;
return false;
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index f94ee3089e01..3aeab9e7e97b 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -621,6 +621,7 @@ struct request_queue {
#define QUEUE_FLAG_RQ_ALLOC_TIME 27/* record rq->alloc_time_ns */
#define QUEUE_FLAG_HCTX_ACTIVE 28 /* at least one blk-mq hctx is active */
#define QUEUE_FLAG_NOWAIT 29 /* device supports NOWAIT */
+#define QUEUE_FLAG_LIMIT_BIO_SIZE 30 /* limit bio size */
#define QUEUE_FLAG_MQ_DEFAULT ((1 << QUEUE_FLAG_IO_STAT) |\
(1 << QUEUE_FLAG_SAME_COMP) | \
@@ -667,6 +668,8 @@ bool blk_queue_flag_test_and_set(unsigned int flag, struct
request_queue *q);
#define blk_queue_fua(q) test_bit(QUEUE_FLAG_FUA, &(q)->queue_flags)
#define
