aio_connect ?

[Ronald F. Guilmette]

In message <20041020031931.GP22681 at funkthat.com>, you wrote:

>Sorry, but there is nothing in FreeBSD that will let you program in the
>method you would like to do...

Well, _if_ there were a full and complet family of aio_*() functions
implemented in the FreeBSD kernel, _then_ I could indeed program in
the style I've described.

>Also, going aio_ as implemented in FreeBSD will be guaranteed to perform
>worse than kqueue/kevent..

I understand that, and I don't care.  As I noted earlier, for some
applications, performance of these particular operations is a non-
issue.

>This is because aio_ requires a kernel thread
>to wait for you instead of your process context..  Currently we are limited
>to only executing 4 aio_ events at once..  This can be increased, but will
>incure a stack for each additional thread you want to run...

That's OK.  I don't mind.  At least I don't think that I mind.  (How big
must the separate event handler stacks be?  If they are only, say, 2kB
apiece, then that's no big deal.  Heck, my lowly desktop machine has a
zillion times that much main memory now!)

>FreeBSD's kernel is inherently syncronous...

Well, surely not entirely. I mean it fields interrupts, right?

>To handle what you want to do, we would need to completely rearchitect
>the FreeBSD kernel to make more things asyncronous..

I was under the impression that a lot of work had already gone in that
general direction in order to support SMP.  No?

>Going async can improve things, and with it, makes implementing a sync
>interface easy on top of it...

Yes.  (I realized myself last night that in theory, read(2) and write(2)
could be implemented, entirely in userland, on top of aio_read() and
aio_write() respectively.)

>So the short of it is, no, FreeBSD at a low level does not support
>it...

Oh well.  It didn't hurt to ask.

>Now, I know this isn't what you want, but I usually make my kevent
>use appear as if it's async...  I use the udata pointer point to a
>struct which starts with a function pointer...  Then when I get events
>back from kevent, I just have code that loops over the events, and calls
>the associated function pointer.. simulating a signal...

I understand.  Your event loop is really an event/dispatch loop.

>Hope this helps...

Well, you have certainly helped to clarify for me the various reasons
why it might be less than a good idea to use aio_*() function calls,
in abundance, on the current FreeBSD kernel.  For that I do thank you.