Currently a full set of static requests are allocated per hw queue per
tagset when shared sbitmap is used.
However, only tagset->queue_depth number of requests may be active at
any given time. As such, only tagset->queue_depth number of static
requests are required.
The same goes for using an IO scheduler, which allocates a full set of
static requests per hw queue per request queue.
This series changes shared sbitmap support by using a shared tags per
tagset and request queue. Ming suggested something along those lines in
v1 review. In using a shared tags, the static rqs also become shared,
reducing the number of sets of static rqs, reducing memory usage.
Patch "blk-mq: Use shared tags for shared sbitmap support" is a bit big,
and could potentially be broken down. But then maintaining ability to
bisect becomes harder and each sub-patch would get more convoluted.
For megaraid sas driver on my 128-CPU arm64 system with 1x SATA disk, we
save approx. 300MB(!) [370MB -> 60MB]
Baseline is 1b2d1439fc25 (block/for-next) Merge branch 'for-5.16/io_uring'
into for-next
Changes since v4:
- Add Hannes' and Ming's RB tags (thanks!) - but please check 12/14 rework
- Add patch to change "shared sbitmap" naming to "shared tags"
- Rebase "block: Rename BLKDEV_MAX_RQ -> BLKDEV_DEFAULT_RQ"
Changes since v3:
- Fix transient error handling issue in 05/13
- Add Hannes RB tags (thanks!)
Changes since v2:
- Make blk_mq_clear_rq_mapping() static again
- Various function renaming for conciseness and consistency
- Add/refactor alloc/free map and rqs function
- Drop the new blk_mq_ops init_request method in favour of passing an
invalid HW queue index for shared sbitmap
- Add patch to not clear rq mapping for driver tags
- Remove blk_mq_init_bitmap_tags()
- Add some more RB tags (thanks!)
Changes since v1:
- Switch to use blk_mq_tags for shared sbitmap
- Add new blk_mq_ops init request callback
- Add some RB tags (thanks!)
John Garry (14):
blk-mq: Change rqs check in blk_mq_free_rqs()
block: Rename BLKDEV_MAX_RQ -> BLKDEV_DEFAULT_RQ
blk-mq: Relocate shared sbitmap resize in blk_mq_update_nr_requests()
blk-mq: Invert check in blk_mq_update_nr_requests()
blk-mq-sched: Rename blk_mq_sched_alloc_{tags -> map_and_rqs}()
blk-mq-sched: Rename blk_mq_sched_free_{requests -> rqs}()
blk-mq: Pass driver tags to blk_mq_clear_rq_mapping()
blk-mq: Don't clear driver tags own mapping
blk-mq: Add blk_mq_tag_update_sched_shared_sbitmap()
blk-mq: Add blk_mq_alloc_map_and_rqs()
blk-mq: Refactor and rename blk_mq_free_map_and_{requests->rqs}()
blk-mq: Use shared tags for shared sbitmap support
blk-mq: Stop using pointers for blk_mq_tags bitmap tags
blk-mq: Change shared sbitmap naming to shared tags
block/bfq-iosched.c | 4 +-
block/blk-core.c | 6 +-
block/blk-mq-debugfs.c | 8 +-
block/blk-mq-sched.c | 118 +++++++++++-------------
block/blk-mq-sched.h | 4 +-
block/blk-mq-tag.c | 135 ++++++++++------------------
block/blk-mq-tag.h | 16 ++--
block/blk-mq.c | 198 +++++++++++++++++++++++------------------
block/blk-mq.h | 36 ++++----
block/blk.h | 2 +-
block/elevator.c | 2 +-
block/kyber-iosched.c | 4 +-
block/mq-deadline.c | 2 +-
drivers/block/rbd.c | 2 +-
include/linux/blk-mq.h | 17 ++--
include/linux/blkdev.h | 5 +-
16 files changed, 262 insertions(+), 297 deletions(-)
--
2.26.2
