Re: [PATCH v3 00/15] io_uring: add Linux io_uring AIO engine

[Stefano Garzarella]

The series LGTM, just some comments on patches 4 and 8.

I succefully tried iotests on raw and qcow2 with io_uring, so

Acked-by: Stefano Garzarella <address@hidden>

Thanks,
Stefano

On Wed, Dec 18, 2019 at 04:32:13PM +0000, Stefan Hajnoczi wrote:
> v12:
>  * Reword BlockdevAioOptions QAPI schema commit description [Markus]
>  * Increase QAPI "Since: 4.2" to "Since: 5.0"
>  * Explain rationale for io_uring stubs in commit description [Kevin]
>  * Tried to use file.aio=io_uring instead of BDRV_O_IO_URING but it's really
>    hard to make qemu-iotests work.  Tests build blkdebug: and other graphs so
>    the syntax for io_uring is dependent on the test case.  I scrapped this
>    approach and went back to a global flag.
> 
> v11:
>  * Drop fd registration because it breaks QEMU's file locking and will need to
>    be resolved in a separate patch series
>  * Drop line-wrapping changes that accidentally broke several qemu-iotests
> 
> v10:
>  * Dropped kernel submission queue polling, it requires root and has 
> additional
>    limitations.  It should be benchmarked and considered for inclusion later,
>    maybe even together with kernel side changes.
>  * Add io_uring_register_files() return value to trace_luring_fd_register()
>  * Fix indentation in luring_fd_unregister()
>  * Set s->fd_reg.fd_array to NULL after g_free() to avoid dangling pointers
>  * Simplify fd registration code
>  * Add luring_fd_unregister() and call it from file-posix.c to prevent
>    fd leaks
>  * Add trace_luring_fd_unregister() trace event
>  * Add missing space to qemu-img command-line documentation
>  * Update MAINTAINERS file [Julia]
>  * Rename MAX_EVENTS to MAX_ENTRIES [Julia]
>  * Define ioq_submit() before callers so the prototype isn't necessary [Julia]
>  * Declare variables at the beginning of the block in luring_init() [Julia]
> 
> This patch series is based on Aarushi Mehta's v9 patch series written for
> Google Summer of Code 2019:
> 
>   https://lists.gnu.org/archive/html/qemu-devel/2019-08/msg00179.html
> 
> It adds a new AIO engine that uses the new Linux io_uring API.  This is the
> successor to Linux AIO with a number of improvements:
> 1. Both O_DIRECT and buffered I/O work
> 2. fdatasync(2) is supported (no need for a separate thread pool!)
> 3. True async behavior so the syscall doesn't block (Linux AIO got there to 
> some degree...)
> 4. Advanced performance optimizations are available (file registration, memory
>    buffer registration, completion polling, submission polling).
> 
> Since Aarushi has been busy, I have taken up this patch series.  Booting a
> guest works with -drive aio=io_uring and -drive aio=io_uring,cache=none with a
> raw file on XFS.
> 
> I currently recommend using -drive aio=io_uring only with host block devices
> (like NVMe devices).  As of Linux v5.4-rc1 I still hit kernel bugs when using
> image files on ext4 or XFS.
> 
> Aarushi Mehta (15):
>   configure: permit use of io_uring
>   qapi/block-core: add option for io_uring
>   block/block: add BDRV flag for io_uring
>   block/io_uring: implements interfaces for io_uring
>   stubs: add stubs for io_uring interface
>   util/async: add aio interfaces for io_uring
>   blockdev: adds bdrv_parse_aio to use io_uring
>   block/file-posix.c: extend to use io_uring
>   block: add trace events for io_uring
>   block/io_uring: adds userspace completion polling
>   qemu-io: adds option to use aio engine
>   qemu-img: adds option to use aio engine for benchmarking
>   qemu-nbd: adds option for aio engines
>   tests/qemu-iotests: enable testing with aio options
>   tests/qemu-iotests: use AIOMODE with various tests
> 
>  MAINTAINERS                   |   9 +
>  block.c                       |  22 ++
>  block/Makefile.objs           |   3 +
>  block/file-posix.c            |  95 ++++++--
>  block/io_uring.c              | 433 ++++++++++++++++++++++++++++++++++
>  block/trace-events            |  12 +
>  blockdev.c                    |  12 +-
>  configure                     |  27 +++
>  include/block/aio.h           |  16 +-
>  include/block/block.h         |   2 +
>  include/block/raw-aio.h       |  12 +
>  qapi/block-core.json          |   4 +-
>  qemu-img-cmds.hx              |   4 +-
>  qemu-img.c                    |  11 +-
>  qemu-img.texi                 |   5 +-
>  qemu-io.c                     |  25 +-
>  qemu-nbd.c                    |  12 +-
>  qemu-nbd.texi                 |   4 +-
>  stubs/Makefile.objs           |   1 +
>  stubs/io_uring.c              |  32 +++
>  tests/qemu-iotests/028        |   2 +-
>  tests/qemu-iotests/058        |   2 +-
>  tests/qemu-iotests/089        |   4 +-
>  tests/qemu-iotests/091        |   4 +-
>  tests/qemu-iotests/109        |   2 +-
>  tests/qemu-iotests/147        |   5 +-
>  tests/qemu-iotests/181        |   8 +-
>  tests/qemu-iotests/183        |   4 +-
>  tests/qemu-iotests/185        |  10 +-
>  tests/qemu-iotests/200        |   2 +-
>  tests/qemu-iotests/201        |   8 +-
>  tests/qemu-iotests/check      |  15 +-
>  tests/qemu-iotests/common.rc  |  14 ++
>  tests/qemu-iotests/iotests.py |  12 +-
>  util/async.c                  |  36 +++
>  35 files changed, 793 insertions(+), 76 deletions(-)
>  create mode 100644 block/io_uring.c
>  create mode 100644 stubs/io_uring.c
> 
> -- 
> 2.23.0
> 
>