• Jens Axboe's avatar
    io_uring: use poll driven retry for files that support it · d7718a9d
    Jens Axboe authored
    Currently io_uring tries any request in a non-blocking manner, if it can,
    and then retries from a worker thread if we get -EAGAIN. Now that we have
    a new and fancy poll based retry backend, use that to retry requests if
    the file supports it.
    
    This means that, for example, an IORING_OP_RECVMSG on a socket no longer
    requires an async thread to complete the IO. If we get -EAGAIN reading
    from the socket in a non-blocking manner, we arm a poll handler for
    notification on when the socket becomes readable. When it does, the
    pending read is executed directly by the task again, through the io_uring
    task work handlers. Not only is this faster and more efficient, it also
    means we're not generating potentially tons of async threads that just
    sit and block, waiting for the IO to complete.
    
    The feature is marked with IORING_FEAT_FAST_POLL, meaning that async
    pollable IO is fast, and that poll<link>other_op is fast as well.
    Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    d7718a9d
io_uring.c 175 KB