Re: [RFC] zero-copy extensions for rsockets

[Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>]

On Tue, Jul 31, 2012 at 08:33:49PM +0000, Hefty, Sean wrote:
> > This looks very similar to the libaio interface..
> 
> I did look at aio.  It may be possible to use aio context in place
> of ioq, and I'm open to that.  I was actually modeling ioq more
> after epoll than aio.  It just seemed simpler to treat an ioq as a
> standard fd.

libaio is designed to be used along with an eventfd that provides the
epoll like semantics you are talking about. Each time you call
io_submit you can call io_set_eventfd() on the iocb and the aio engine
will trigger that eventfd when the IO completes. poll or epoll on the
eventfd fd.

> My concern is that supporting a more flexible API, like aoi, would
> effectively result in losing some desirable feature handling
> completions, such as kernel bypass or reducing interrupts.  With
> aio, I'm unsure about the impact of supporting callback
> notifications and the selection of each aio context on a per request
> basis.

I'm not sure what you are refering to here? Are you mixing up POSIX
aio with libaio? They are totally different. libaio has no callback
notification mechanism, just io_getevents.

Jason
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