Re: [Qemu-devel] [PATCH v4 0/9] Add support for io_uring

[Sergio Lopez]

Aarushi Mehta <address@hidden> writes:

> This patch series adds support for the newly developed io_uring Linux AIO
> interface. Linux io_uring is faster than Linux's AIO asynchronous I/O code,
> offers efficient buffered asynchronous I/O support, the ability to do I/O
> without performing a system call via polled I/O, and other efficiency 
> enhancements.
>
> Testing it requires a host kernel (5.1+) and the liburing library.
> Use the option -drive aio=io_uring to enable it.
>
> v4:
> - Add error handling
> - Add trace events
> - Remove aio submission based code
>
> v3:
> - Fix major errors in io_uring (sorry)
> - Option now enumerates for CONFIG_LINUX_IO_URING
> - pkg config support added
>
> Aarushi Mehta (9):
>   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: accept io_uring as option
>   block/file-posix.c: extend to use io_uring
>   block: add trace events for io_uring
>
>  MAINTAINERS             |   8 +
>  block/Makefile.objs     |   3 +
>  block/file-posix.c      |  85 +++++++++--
>  block/io_uring.c        | 325 ++++++++++++++++++++++++++++++++++++++++
>  block/trace-events      |   8 +
>  blockdev.c              |   4 +-
>  configure               |  27 ++++
>  include/block/aio.h     |  16 +-
>  include/block/block.h   |   1 +
>  include/block/raw-aio.h |  12 ++
>  qapi/block-core.json    |   4 +-
>  stubs/Makefile.objs     |   1 +
>  stubs/io_uring.c        |  32 ++++
>  util/async.c            |  36 +++++
>  14 files changed, 543 insertions(+), 19 deletions(-)
>  create mode 100644 block/io_uring.c
>  create mode 100644 stubs/io_uring.c

Hi Aarushi,

I gave this version of the patchset a try, and found that IO hangs when
the device is assigned to an IOThread. Sometimes is able to serve a few
requests getting through the Guest OS boot process, to hang the moment
you try generate some IO on the device, while others it hangs when Linux
tries to read the partitions from the device.

I'm starting QEMU this way:

./x86_64-softmmu/qemu-system-x86_64 -enable-kvm -name rhel80,debug-threads=on 
-m 2g -smp 4 -object iothread,id=iothread0 -blockdev 
node-name=rhel80,driver=qcow2,file.driver=file,file.filename=/home/VirtualMachines/rhel80.qcow2
 -device virtio-blk,drive=rhel80 -serial tcp::6667,server,nowait -qmp 
tcp::6668,server,nowait -nographic -net user,hostfwd=tcp::6666-:22 -net 
nic,model=virtio -device virtio-rng -drive 
file=/dev/nullb0,format=raw,cache=none,aio=io_uring,if=none,id=test -device 
virtio-blk,drive=test,iothread=iothread0

Could you please take a look at this issue?

Thanks,
Sergio.

signature.asc
Description: PGP signature