Re: [LSF/MM TOPIC] async buffered diskio read for userspace apps

[Jeff Moyer <jmoyer@redhat.com>]

Milosz Tanski <milosz@adfin.com> writes:

> I would like to talk about enhancing the user interfaces for doing
> async buffered disk IO for userspace applications. There's a whole
> class of distributed web applications (most new applications today)
> that would benefit from such an API. Most of them today rely on
> cobbling one together in user space using a threadpool.
>
> The current in kernel AIO interfaces that only support DIRECTIO, they
> were generally designed by and for big database vendors. The consensus
> is that the current AIO interfaces usually lead to decreased
> performance for those app.
>
> I've been developing a new read syscall that allows non-blocking
> diskio read (provided that data is in the page cache). It's analogous
> to what exists today in the network world with recvmsg with MSG_NOWAIT
> flag. The work has been previously described by LWN here:
> https://lwn.net/Articles/612483/
>
> Previous attempts (over the last 12+ years) at non-blocking buffered
> diskio has stalled due to their complexity. I would like to talk about
> the problem, my solution, and get feedback on the course of action.

This email seems to conflate async I/O and non-blocking I/O.  Could you
please be more specific about what you're proposing to talk about?  Is
it just the non-blocking read support?

Cheers,
Jeff

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