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* [PATCHv2 0/7] dma mapping optimisations
@ 2022-08-02 19:36 Keith Busch
  2022-08-02 19:36 ` [PATCHv2 1/7] blk-mq: add ops to dma map bvec Keith Busch
                   ` (7 more replies)
  0 siblings, 8 replies; 12+ messages in thread
From: Keith Busch @ 2022-08-02 19:36 UTC (permalink / raw)
  To: linux-nvme, linux-block, io-uring, linux-fsdevel
  Cc: axboe, hch, Alexander Viro, Kernel Team, Keith Busch

From: Keith Busch <[email protected]>

Changes since v1:

  Mapping/unmapping goes through file ops instead of block device ops.
  This abstracts io_uring from knowing about specific block devices. For
  this series, the only "file system" implementing the ops is the raw
  block device, but should be easy enough to add more filesystems if
  needed.

  Mapping register requires io_uring fixed files. This ties the
  registered buffer's lifetime to no more than the file it was
  registered with.

Summary:

A typical journey a user address takes for a read or write to a block
device undergoes various represenations for every IO. Each consumes
memory and CPU cycles. When the backing storage is NVMe, the sequence
looks something like the following:

  __user void *
  struct iov_iter
  struct pages[]
  struct bio_vec[]
  struct scatterlist[]
  __le64[]

Applications will often use the same buffer for many IO, though, so
these potentially costly per-IO transformations to reach the exact same
hardware descriptor can be skipped.

The io_uring interface already provides a way for users to register
buffers to get to the 'struct bio_vec[]'. That still leaves the
scatterlist needed for the repeated dma_map_sg(), then transform to
nvme's PRP list format.

This series takes the registered buffers a step further. A block driver
can implement a new .dma_map() callback to complete the representation
to the hardware's DMA mapped address, and return a cookie so a user can
reference it later for any given IO. When used, the block stack can skip
significant amounts of code, improving CPU utilization, and, if not
bandwidth limited, IOPs.

The implementation is currently limited to mapping a registered buffer
to a single file.

Keith Busch (7):
  blk-mq: add ops to dma map bvec
  file: add ops to dma map bvec
  iov_iter: introduce type for preregistered dma tags
  block: add dma tag bio type
  io_uring: introduce file slot release helper
  io_uring: add support for dma pre-mapping
  nvme-pci: implement dma_map support

 block/bdev.c                   |  20 +++
 block/bio.c                    |  25 ++-
 block/blk-merge.c              |  19 +++
 block/fops.c                   |  20 +++
 drivers/nvme/host/pci.c        | 302 +++++++++++++++++++++++++++++++--
 fs/file.c                      |  15 ++
 include/linux/bio.h            |  21 ++-
 include/linux/blk-mq.h         |  24 +++
 include/linux/blk_types.h      |   6 +-
 include/linux/blkdev.h         |  16 ++
 include/linux/fs.h             |  20 +++
 include/linux/io_uring_types.h |   2 +
 include/linux/uio.h            |   9 +
 include/uapi/linux/io_uring.h  |  12 ++
 io_uring/filetable.c           |  34 ++--
 io_uring/filetable.h           |  10 +-
 io_uring/io_uring.c            | 137 +++++++++++++++
 io_uring/net.c                 |   2 +-
 io_uring/rsrc.c                |  26 +--
 io_uring/rsrc.h                |  10 +-
 io_uring/rw.c                  |   2 +-
 lib/iov_iter.c                 |  24 ++-
 22 files changed, 704 insertions(+), 52 deletions(-)

-- 
2.30.2


^ permalink raw reply	[flat|nested] 12+ messages in thread

end of thread, other threads:[~2022-08-04 16:42 UTC | newest]

Thread overview: 12+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2022-08-02 19:36 [PATCHv2 0/7] dma mapping optimisations Keith Busch
2022-08-02 19:36 ` [PATCHv2 1/7] blk-mq: add ops to dma map bvec Keith Busch
2022-08-02 19:36 ` [PATCHv2 2/7] file: " Keith Busch
2022-08-02 19:36 ` [PATCHv2 3/7] iov_iter: introduce type for preregistered dma tags Keith Busch
2022-08-02 19:36 ` [PATCHv2 4/7] block: add dma tag bio type Keith Busch
2022-08-02 19:36 ` [PATCHv2 5/7] io_uring: introduce file slot release helper Keith Busch
2022-08-02 19:36 ` [PATCHv2 6/7] io_uring: add support for dma pre-mapping Keith Busch
2022-08-02 23:25   ` Ammar Faizi
2022-08-02 19:36 ` [PATCHv2 7/7] nvme-pci: implement dma_map support Keith Busch
2022-08-03 20:52 ` [PATCHv2 0/7] dma mapping optimisations Jens Axboe
2022-08-04 16:28   ` Keith Busch
2022-08-04 16:42     ` Jens Axboe

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