[PATCH V4 00/27] ublk: add UBLK_F_BATCH_IO

[Ming Lei <ming.lei@redhat.com>]

Hello,

This patchset adds UBLK_F_BATCH_IO feature for communicating between kernel and ublk
server in batching way:

- Per-queue vs Per-I/O: Commands operate on queues rather than individual I/Os

- Batch processing: Multiple I/Os are handled in single operation

- Multishot commands: Use io_uring multishot for reducing submission overhead

- Flexible task assignment: Any task can handle any I/O (no per-I/O daemons)

- Better load balancing: Tasks can adjust their workload dynamically

- help for future optimizations:
	- blk-mq batch tags free
  	- support io-poll
	- per-task batch for avoiding per-io lock
	- fetch command priority

- simplify command cancel process with per-queue lock

selftest are provided.


Performance test result(IOPS) on V3:

- page copy

tools/testing/selftests/ublk//kublk add -t null -q 16 [-b]

- zero copy(--auto_zc)
tools/testing/selftests/ublk//kublk add -t null -q 16 --auto_zc [-b]

- IO test
taskset -c 0-31 fio/t/io_uring -p0 -n $JOBS -r 30 /dev/ublkb0

1) 16 jobs IO
- page copy:  			37.77M vs. 42.40M(BATCH_IO), +12%
- zero copy(--auto_zc): 42.83M vs. 44.43M(BATCH_IO), +3.7%


2) single job IO
- page copy:  			2.54M vs. 2.6M(BATCH_IO),   +2.3%
- zero copy(--auto_zc): 3.13M vs. 3.35M(BATCH_IO),  +7%


V4:
	- fix handling in case of running out of mshot buffer, request has to
	  be un-prepared for zero copy
	- don't expose unused tag to userspace
	- replace fixed buffer with plain user buffer for
	  UBLK_U_IO_PREP_IO_CMDS and UBLK_U_IO_COMMIT_IO_CMDS
	- replace iov iterator with plain copy_from_user() for
	  ublk_walk_cmd_buf(), code is simplified with performance improvement
	- don't touch sqe->len for UBLK_U_IO_PREP_IO_CMDS and
	  UBLK_U_IO_COMMIT_IO_CMDS(Caleb Sander Mateos)
	- use READ_ONCE() for access sqe->addr (Caleb Sander Mateos)
	- all kinds of patch style fix(Caleb Sander Mateos)
	- inline __kfifo_alloc() (Caleb Sander Mateos)


V3:
	- rebase on for-6.19/block
	- use blk_mq_end_request_batch() to free requests in batch, only for
	  page copy
	- fix one IO hang issue because of memory barrier order, comments on
	the memory barrier pairing
	- add NUMA ware kfifo_alloc_node()
	- fix one build warning reported by 0-DAY CI
	- selftests improvement & fix

V2:
	- ublk_config_io_buf() vs. __ublk_fetch() order
	- code style clean
	- use READ_ONCE() to cache sqe data because sqe copy becomes
	  conditional recently
	- don't use sqe->len for UBLK_U_IO_PREP_IO_CMDS &
	  UBLK_U_IO_COMMIT_IO_CMDS
	- fix one build warning
	- fix build_user_data()
	- run performance analysis, and find one bug in
	  io_uring_cmd_buffer_select(), fix is posted already

Ming Lei (27):
  kfifo: add kfifo_alloc_node() helper for NUMA awareness
  ublk: add parameter `struct io_uring_cmd *` to
    ublk_prep_auto_buf_reg()
  ublk: add `union ublk_io_buf` with improved naming
  ublk: refactor auto buffer register in ublk_dispatch_req()
  ublk: pass const pointer to ublk_queue_is_zoned()
  ublk: add helper of __ublk_fetch()
  ublk: define ublk_ch_batch_io_fops for the coming feature F_BATCH_IO
  ublk: prepare for not tracking task context for command batch
  ublk: add new batch command UBLK_U_IO_PREP_IO_CMDS &
    UBLK_U_IO_COMMIT_IO_CMDS
  ublk: handle UBLK_U_IO_PREP_IO_CMDS
  ublk: handle UBLK_U_IO_COMMIT_IO_CMDS
  ublk: add io events fifo structure
  ublk: add batch I/O dispatch infrastructure
  ublk: add UBLK_U_IO_FETCH_IO_CMDS for batch I/O processing
  ublk: abort requests filled in event kfifo
  ublk: add new feature UBLK_F_BATCH_IO
  ublk: document feature UBLK_F_BATCH_IO
  ublk: implement batch request completion via
    blk_mq_end_request_batch()
  selftests: ublk: fix user_data truncation for tgt_data >= 256
  selftests: ublk: replace assert() with ublk_assert()
  selftests: ublk: add ublk_io_buf_idx() for returning io buffer index
  selftests: ublk: add batch buffer management infrastructure
  selftests: ublk: handle UBLK_U_IO_PREP_IO_CMDS
  selftests: ublk: handle UBLK_U_IO_COMMIT_IO_CMDS
  selftests: ublk: handle UBLK_U_IO_FETCH_IO_CMDS
  selftests: ublk: add --batch/-b for enabling F_BATCH_IO
  selftests: ublk: support arbitrary threads/queues combination

 Documentation/block/ublk.rst                  |   60 +-
 drivers/block/ublk_drv.c                      | 1312 +++++++++++++++--
 include/linux/kfifo.h                         |   34 +-
 include/uapi/linux/ublk_cmd.h                 |   85 ++
 lib/kfifo.c                                   |    8 +-
 tools/testing/selftests/ublk/Makefile         |    7 +-
 tools/testing/selftests/ublk/batch.c          |  604 ++++++++
 tools/testing/selftests/ublk/common.c         |    2 +-
 tools/testing/selftests/ublk/file_backed.c    |   11 +-
 tools/testing/selftests/ublk/kublk.c          |  143 +-
 tools/testing/selftests/ublk/kublk.h          |  195 ++-
 tools/testing/selftests/ublk/null.c           |   18 +-
 tools/testing/selftests/ublk/stripe.c         |   17 +-
 .../testing/selftests/ublk/test_generic_14.sh |   32 +
 .../testing/selftests/ublk/test_generic_15.sh |   30 +
 .../testing/selftests/ublk/test_generic_16.sh |   30 +
 .../testing/selftests/ublk/test_stress_06.sh  |   45 +
 .../testing/selftests/ublk/test_stress_07.sh  |   44 +
 tools/testing/selftests/ublk/utils.h          |   64 +
 19 files changed, 2563 insertions(+), 178 deletions(-)
 create mode 100644 tools/testing/selftests/ublk/batch.c
 create mode 100755 tools/testing/selftests/ublk/test_generic_14.sh
 create mode 100755 tools/testing/selftests/ublk/test_generic_15.sh
 create mode 100755 tools/testing/selftests/ublk/test_generic_16.sh
 create mode 100755 tools/testing/selftests/ublk/test_stress_06.sh
 create mode 100755 tools/testing/selftests/ublk/test_stress_07.sh

-- 
2.47.0