From: Changheun Lee <nanich.lee@samsung.com>
To: Johannes.Thumshirn@wdc.com, axboe@kernel.dk,
damien.lemoal@wdc.com, asml.silence@gmail.com,
patchwork-bot@kernel.org, osandov@fb.com,
linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
ming.lei@redhat.com, tj@kernel.org, tom.leiming@gmail.com
Cc: jisoo2146.oh@samsung.com, junho89.kim@samsung.com,
mj0123.lee@samsung.com, seunghwan.hyun@samsung.com,
sookwan7.kim@samsung.com, woosung2.lee@samsung.com,
yt0928.kim@samsung.com, Changheun Lee <nanich.lee@samsung.com>
Subject: [PATCH v2] bio: limit bio max size.
Date: Thu, 21 Jan 2021 09:58:03 +0900 [thread overview]
Message-ID: <20210121005803.26052-1-nanich.lee@samsung.com> (raw)
In-Reply-To: CGME20210121011324epcas1p3a213069e873fd324a7ce3188558f0782@epcas1p3.samsung.com
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 memory address is
continued phsycally. it makes some delay to submit until merge complete.
bio max size should be limited as a proper size.
When 32MB chunk read with direct I/O option is coming from userspace,
kernel behavior is below now. 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 <nanich.lee@samsung.com>
---
block/bio.c | 17 ++++++++++++++++-
include/linux/bio.h | 13 +++----------
include/linux/blk_types.h | 1 +
3 files changed, 20 insertions(+), 11 deletions(-)
diff --git a/block/bio.c b/block/bio.c
index 1f2cc1fbe283..027503c2e2e7 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -284,9 +284,24 @@ void bio_init(struct bio *bio, struct bio_vec *table,
bio->bi_io_vec = table;
bio->bi_max_vecs = max_vecs;
+ bio->bi_max_size = UINT_MAX;
}
EXPORT_SYMBOL(bio_init);
+void bio_set_dev(struct bio *bio, struct block_device *bdev)
+{
+ if (bio->bi_disk != bdev->bd_disk)
+ bio_clear_flag(bio, BIO_THROTTLED);
+
+ bio->bi_disk = bdev->bd_disk;
+ bio->bi_partno = bdev->bd_partno;
+ bio->bi_max_size = blk_queue_get_max_sectors(bio->bi_disk->queue,
+ bio_op(bio)) << SECTOR_SHIFT;
+
+ bio_associate_blkg(bio);
+}
+EXPORT_SYMBOL(bio_set_dev);
+
/**
* bio_reset - reinitialize a bio
* @bio: bio to reset
@@ -877,7 +892,7 @@ 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->bi_max_size - len)
*same_page = false;
return false;
}
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 1edda614f7ce..b9803e80c259 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->bi_max_size - len)
return true;
return false;
@@ -482,20 +482,13 @@ extern struct bio_vec *bvec_alloc(gfp_t, int, unsigned long *, mempool_t *);
extern void bvec_free(mempool_t *, struct bio_vec *, unsigned int);
extern unsigned int bvec_nr_vecs(unsigned short idx);
extern const char *bio_devname(struct bio *bio, char *buffer);
-
-#define bio_set_dev(bio, bdev) \
-do { \
- if ((bio)->bi_disk != (bdev)->bd_disk) \
- bio_clear_flag(bio, BIO_THROTTLED);\
- (bio)->bi_disk = (bdev)->bd_disk; \
- (bio)->bi_partno = (bdev)->bd_partno; \
- bio_associate_blkg(bio); \
-} while (0)
+extern void bio_set_dev(struct bio *bio, struct block_device *bdev);
#define bio_copy_dev(dst, src) \
do { \
(dst)->bi_disk = (src)->bi_disk; \
(dst)->bi_partno = (src)->bi_partno; \
+ (dst)->bi_max_size = (src)->bi_max_size;\
bio_clone_blkg_association(dst, src); \
} while (0)
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 866f74261b3b..e5dd5b7d8fc1 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -270,6 +270,7 @@ struct bio {
*/
unsigned short bi_max_vecs; /* max bvl_vecs we can hold */
+ unsigned int bi_max_size; /* max data size we can hold */
atomic_t __bi_cnt; /* pin count */
--
2.28.0
next parent reply other threads:[~2021-01-21 1:21 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20210121011324epcas1p3a213069e873fd324a7ce3188558f0782@epcas1p3.samsung.com>
2021-01-21 0:58 ` Changheun Lee [this message]
2021-01-21 1:53 ` [PATCH v2] bio: limit bio max size Damien Le Moal
[not found] ` <CGME20210121095138epcas1p125bb1879c65fafe4636d71b8ab5f90cd@epcas1p1.samsung.com>
2021-01-21 9:36 ` Changheun Lee
2021-01-21 10:17 ` Damien Le Moal
[not found] ` <CGME20210121113928epcas1p13c9dd6d1322979a977f24ded689b38de@epcas1p1.samsung.com>
2021-01-21 11:24 ` Changheun Lee
2021-01-21 5:23 ` kernel test robot
2021-01-22 3:45 ` Ming Lei
[not found] ` <CGME20210125015636epcas1p344b530317fe3379914449197ad591eff@epcas1p3.samsung.com>
2021-01-25 1:41 ` Changheun Lee
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