[mpich-discuss] ROMIO and asynchronous MPI-IO

[Ahmad Tarraf]

Dear ROMIO developers,

It is hard to find any literature or documentation about the 
asynchronous implementation ROMIO (or ADIO) use. I have few questions 
and It would be great if you can answer them:

 1. How does ROMIO implement asynchronous I/O? I mean do you use
    POSIX-AIO, native Linux kernel AIO (io_submit,..),  io_uring, or
    anything else? If I debug my code at our Clusters with gdb, I can
    see that POSIX-AIO is used. But is this on all systems so?
 2. When and how does asynchronous I/O progress occur? Do you span
    multiple I/O threads for a rank? Is this related to variable
    MPICH_ASYNC_PROGRESS? Again with gdb, I can see that several
    asynchronous write requests by the same MPI rank are handled
    successively by a single thread.
 3. Is there any related recent publication is can use to cite? I didn't
    find anything related to the implementation of asynchronous MPI-IO,
    except this:
    https://web.cels.anl.gov/~thakur/papers/grequest-redesign.pdf. But
    is it not outdated?


Best regards,

Ahmad
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