Re: [Qemu-devel] Re: [PATCH][RFC] Refactor AIO to allow multiple AIO implementations

[Jamie Lokier <jamie@shareable.org>]

Gerd Hoffmann wrote:
> > (I think the best
> > route is a thread-pool based implementation).
> 
> Not sure about that.  linux-aio would have the advantage that the kernel
> knows about all the requests in flight and probably can do a better job
> on I/O ordering and scheduling then.  But once we can have multiple
> different implementations we can just try ;)

Won't posix-aio give the same info to the kernel when used with a
sufficiently avante-garde Linux distro?

I'm under the impression that linux-aio is better in every way, as
I think Anthony Liguori posted a while back:

>>>  Threads are a poor substitute for a proper AIO interface.
>>>  linux-aio gives you everything you could possibly want in an
>>>  interface since it allows you to submit multiple vectored operations
>>>  in a single syscall, use an fd to signal request completion,
>>>  complete multiple requests in a single syscall, and inject barriers
>>>  via fdsync.

But knowing about request in flight, I/O ordering etc. seem equally
available via posix-aio on a distro where that calls linux-aio
(i.e. not the Glibc implementation).

-- Jamie