[v5,0/2] block/dm: support bio polling

Message

Mike Snitzer March 5, 2022, 2:08 a.m. UTC

Hi,

I've rebased Ming's latest [1] ontop of dm-5.18 [2] (which is based on
for-5.18/block). End result available in dm-5.18-biopoll branch [3]

These changes add bio polling support to DM.  Tested with linear and
striped DM targets.

IOPS improvement was ~5% on my baremetal system with a single Intel
Optane NVMe device (555K hipri=1 vs 525K hipri=0).

Ming has seen better improvement while testing within a VM:
 dm-linear: hipri=1 vs hipri=0 15~20% iops improvement
 dm-stripe: hipri=1 vs hipri=0 ~30% iops improvement

I'd like to merge these changes via the DM tree when the 5.18 merge
window opens.  The first block patch that adds ->poll_bio to
block_device_operations will need review so that I can take it
through the DM tree.  Reason for going through the DM tree is there
have been some fairly extensive changes queued in dm-5.18 that build
on for-5.18/block.  So I think it easiest to just add the block
depenency via DM tree since DM is first consumer of ->poll_bio

FYI, Ming does have another DM patch [4] that looks to avoid using
hlist but I only just saw it.  bio_split() _is_ involved (see
dm_split_and_process_bio) so I'm not exactly sure where he is going
with that change.  But that is DM-implementation detail that we'll
sort out. Big thing is we need approval for the first block patch to
go to Linus via the DM tree ;)

Thanks,
Mike

[1] https://github.com/ming1/linux/commits/my_v5.18-dm-bio-poll
[2] https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/log/?h=dm-5.18
[3] https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/log/?h=dm-5.18-biopoll
[4] https://github.com/ming1/linux/commit/c107c30e15041ac1ce672f56809961406e2a3e52

v5: remove WARN_ONs in ->poll_bio interface patch. Fixed comment typo
    along the way (found while seeing how other
    block_device_operations are referenced in block's code comments).

Ming Lei (2):
  block: add ->poll_bio to block_device_operations
  dm: support bio polling

 block/blk-core.c       |  14 +++--
 block/genhd.c          |   4 ++
 drivers/md/dm-core.h   |   2 +
 drivers/md/dm-table.c  |  27 +++++++++
 drivers/md/dm.c        | 150 ++++++++++++++++++++++++++++++++++++++++++++++++-
 include/linux/blkdev.h |   2 +
 6 files changed, 191 insertions(+), 8 deletions(-)