RE: aio_connect ?
From: Christopher M. Sedore (cmsedore_at_maxwell.syr.edu)
Date: 10/20/04
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Date: Wed, 20 Oct 2004 17:05:17 -0400 To: "Igor Sysoev" <is@rambler-co.ru>
> From: Igor Sysoev [mailto:is@rambler-co.ru]
> Subject: RE: aio_connect ?
>
> On Wed, 20 Oct 2004, Christopher M. Sedore wrote:
>
> > > While the developing my server nginx, I found the POSIX aio_*
> > > operations
> > > uncomfortable. I do not mean a different programming style, I mean
> > > the aio_read() and aio_write() drawbacks - they have no
> scatter-gather
> > > capabilities (aio_readv/aio_writev) and they require too many
> > > syscalls.
> > > E.g, the reading requires
> > > *) 3 syscalls for ready data: aio_read(), aio_error(),
> aio_return()
> > > *) 5 syscalls for non-ready data: aio_read(), aio_error(),
> > > waiting for notification, then aio_error(), aio_return(),
> > > or if timeout occuired - aio_cancel(), aio_error().
> >
> > This is why I added aio_waitcomplete(). It reduces both
> cases to two
> > syscalls.
>
> As I understand aio_waitcomplete() returns aiocb of any complete AIO
> operation but I need to know the state of the exact AIO,
> namely the last
> aio_read().
Correct, it won't poll, but what state can you get from calling
aio_error() that you don't already know from aio_waitcomplete(). The
operation has either completed (successfully or unsuccessfully) or it
hasn't. If it hasn't you haven't "gotten it back" via aio_waitcomplete,
and if it has, you did. I may be missing something, but how does
aio_error() tell you something that you don't already know?
> I use kqueue to get AIO notifications. If AIO operation would fail
> at the start, will kqueue return notificaiton about this operation ?
I don't think so--IIRC, if you have a parameter problem or the operation
can't be queued, you'll get an error return from aio_read and no kqueue
result. If it is queued, you'll get a kqueue notification.
-Chris
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- Previous message: Ronald F. Guilmette: "Re: aio_connect ?"
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