[RFC 00/16] Introduce ring flexible placement

[Pavel Begunkov <asml.silence@gmail.com>]

This patchset allows the user to put rings and ring headers
into the memory/parameter region and specify offsets where they
should lie.

It solves a problem where the headers are placed before ring entries,
which 1. usually padded wasting memory and using more cache lines
than a smarter placement would need. And 2. it grows the region size
to a non pow2. It's also handy to have a way to put everything into
a single region.

It's implemented for SQ and CQ, but planned to be supported by zcrx
as well. There is a bunch of cleanups (1-13), it'd make sense to
merge some of them separately. It also adds an ability to register
a memory region during setup and not via a registration (Patch 15).
And the placement handling is in Patch 16.

Pavel Begunkov (16):
  io_uring: add helper calculating region byte size
  io_uring: pass sq entires in the params struct
  io_uring: use mem_is_zero to check ring params
  io_uring: move flags check to io_uring_sanitise_params
  io_uring: introduce struct io_ctx_config
  io_uring: split out config init helper
  io_uring: add structure keeping ring offsets
  io_uring: pre-calculate scq offsets
  io_uring: inroduce helper for setting user offset
  io_uring: separate cqe array from headers
  io_uring/region: introduce io_region_slice
  io_uring: convert pointer init to io_region_slice
  io_uring: refactor rings_size()
  io_uring: extract io_create_mem_region
  io_uring: allow creating mem region at setup
  io_uring: introduce SCQ placement

 include/linux/io_uring_types.h |  17 +-
 include/uapi/linux/io_uring.h  |  21 +-
 io_uring/fdinfo.c              |   2 +-
 io_uring/io_uring.c            | 341 +++++++++++++++++++++++----------
 io_uring/io_uring.h            |  34 +++-
 io_uring/memmap.c              |  16 +-
 io_uring/memmap.h              |   7 +
 io_uring/register.c            |  75 ++++----
 8 files changed, 360 insertions(+), 153 deletions(-)

-- 
2.49.0