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 <[email protected]>
---
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 = &bio->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 blk_queue_registered(q) test_bit(QUEUE_FLAG_REGISTERED, &(q)->queue_flags)
#define blk_queue_nowait(q) test_bit(QUEUE_FLAG_NOWAIT, &(q)->queue_flags)
+#define blk_queue_limit_bio_size(q) \
+ test_bit(QUEUE_FLAG_LIMIT_BIO_SIZE, &(q)->queue_flags)
extern void blk_set_pm_only(struct request_queue *q);
extern void blk_clear_pm_only(struct request_queue *q);
--
2.28.0
Add limit_bio_size block sysfs node to limit bio size.
Queue flag QUEUE_FLAG_LIMIT_BIO_SIZE will be set if limit_bio_size is set.
And bio max size will be limited by queue max sectors via
QUEUE_FLAG_LIMIT_BIO_SIZE set.
Signed-off-by: Changheun Lee <[email protected]>
---
Documentation/ABI/testing/sysfs-block | 10 ++++++++++
Documentation/block/queue-sysfs.rst | 7 +++++++
block/blk-sysfs.c | 3 +++
3 files changed, 20 insertions(+)
diff --git a/Documentation/ABI/testing/sysfs-block b/Documentation/ABI/testing/sysfs-block
index e34cdeeeb9d4..86a7b15410cf 100644
--- a/Documentation/ABI/testing/sysfs-block
+++ b/Documentation/ABI/testing/sysfs-block
@@ -316,3 +316,13 @@ Description:
does not complete in this time then the block driver timeout
handler is invoked. That timeout handler can decide to retry
the request, to fail it or to start a device recovery strategy.
+
+What: /sys/block/<disk>/queue/limit_bio_size
+Date: Feb, 2021
+Contact: Changheun Lee <[email protected]>
+Description:
+ (RW) Toggle for set/clear QUEUE_FLAG_LIMIT_BIO_SIZE queue flag.
+ Queue flag QUEUE_FLAG_LIMIT_BIO_SIZE will be set if limit_bio_size
+ is set. And bio max size will be limited by queue max sectors.
+ QUEUE_FLAG_LIMIT_BIO_SIZE will be cleared if limit_bio_size is
+ cleard. And limit of bio max size will be cleard.
diff --git a/Documentation/block/queue-sysfs.rst b/Documentation/block/queue-sysfs.rst
index 2638d3446b79..cd371a821855 100644
--- a/Documentation/block/queue-sysfs.rst
+++ b/Documentation/block/queue-sysfs.rst
@@ -273,4 +273,11 @@ devices are described in the ZBC (Zoned Block Commands) and ZAC
do not support zone commands, they will be treated as regular block devices
and zoned will report "none".
+limit_bio_size (RW)
+-------------------
+This indicates QUEUE_FLAG_LIMIT_BIO_SIZE queue flag value. And
+QUEUE_FLAG_LIMIT_BIO_SIZE can be changed via set(1)/clear(0) this node.
+bio max size will be limited by queue max sectors via set this node. And
+limit of bio max size will be cleard via clear this node.
+
Jens Axboe <[email protected]>, February 2009
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index b513f1683af0..840d97f427e6 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -288,6 +288,7 @@ QUEUE_SYSFS_BIT_FNS(nonrot, NONROT, 1);
QUEUE_SYSFS_BIT_FNS(random, ADD_RANDOM, 0);
QUEUE_SYSFS_BIT_FNS(iostats, IO_STAT, 0);
QUEUE_SYSFS_BIT_FNS(stable_writes, STABLE_WRITES, 0);
+QUEUE_SYSFS_BIT_FNS(limit_bio_size, LIMIT_BIO_SIZE, 0);
#undef QUEUE_SYSFS_BIT_FNS
static ssize_t queue_zoned_show(struct request_queue *q, char *page)
@@ -615,6 +616,7 @@ QUEUE_RW_ENTRY(queue_nonrot, "rotational");
QUEUE_RW_ENTRY(queue_iostats, "iostats");
QUEUE_RW_ENTRY(queue_random, "add_random");
QUEUE_RW_ENTRY(queue_stable_writes, "stable_writes");
+QUEUE_RW_ENTRY(queue_limit_bio_size, "limit_bio_size");
static struct attribute *queue_attrs[] = {
&queue_requests_entry.attr,
@@ -648,6 +650,7 @@ static struct attribute *queue_attrs[] = {
&queue_rq_affinity_entry.attr,
&queue_iostats_entry.attr,
&queue_stable_writes_entry.attr,
+ &queue_limit_bio_size_entry.attr,
&queue_random_entry.attr,
&queue_poll_entry.attr,
&queue_wc_entry.attr,
--
2.28.0
Please feedback to me if more modification is needed to apply. :)
---
Changheun Lee
On Tue, Feb 16, 2021 at 11:00:32AM +0900, Changheun Lee wrote:
> Please feedback to me if more modification is needed to apply. :)
No context here :(
>
> On Tue, Feb 16, 2021 at 11:00:32AM +0900, Changheun Lee wrote:
> > Please feedback to me if more modification is needed to apply. :)
>
> No context here :(
>
I'm so sorry. I missed it.
> 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 <[email protected]>
> ---
> 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 = &bio->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 blk_queue_registered(q) test_bit(QUEUE_FLAG_REGISTERED, &(q)->queue_flags)
> #define blk_queue_nowait(q) test_bit(QUEUE_FLAG_NOWAIT, &(q)->queue_flags)
> +#define blk_queue_limit_bio_size(q) \
> + test_bit(QUEUE_FLAG_LIMIT_BIO_SIZE, &(q)->queue_flags)
>
> extern void blk_set_pm_only(struct request_queue *q);
> extern void blk_clear_pm_only(struct request_queue *q);
> --
> 2.28.0
>
Please feedback to me if more modification is needed to apply. :)
---
Changheun Lee
On Tue, Feb 16, 2021 at 03:42:42PM +0900, Changheun Lee wrote:
> >
> > On Tue, Feb 16, 2021 at 11:00:32AM +0900, Changheun Lee wrote:
> > > Please feedback to me if more modification is needed to apply. :)
> >
> > No context here :(
> >
>
> I'm so sorry. I missed it.
>
> > 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 <[email protected]>
> > ---
> > 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 = &bio->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 blk_queue_registered(q) test_bit(QUEUE_FLAG_REGISTERED, &(q)->queue_flags)
> > #define blk_queue_nowait(q) test_bit(QUEUE_FLAG_NOWAIT, &(q)->queue_flags)
> > +#define blk_queue_limit_bio_size(q) \
> > + test_bit(QUEUE_FLAG_LIMIT_BIO_SIZE, &(q)->queue_flags)
> >
> > extern void blk_set_pm_only(struct request_queue *q);
> > extern void blk_clear_pm_only(struct request_queue *q);
> > --
> > 2.28.0
> >
>
> Please feedback to me if more modification is needed to apply. :)
It's the middle of the merge window, no maintainers can add anything new
to their trees, so please wait until after 5.12-rc1 is out before we can
do anything...
thanks,
greg k-h