[Mono-list] threads and Async Socket methods

Gonzalo Paniagua Javier gonzalo@ximian.com
Fri, 07 May 2004 21:16:07 +0200

El vie, 07-05-2004 a las 20:59, P Oscar Boykin escribió:
> Thanks for pointing out this article.
> This appears to be my problem:
> When I have enough sockets waiting on a BeginReceive, I cannot do
> any other Async method.  I guess the worker queue gets filled with the
> BeginReceive calls, and then BeginSend calls cannot get through.
> For our work, the limit of 25 ThreadPool threads waiting on tcp sockets
> is just not going to work.
> It seems like there are two options here:
> 1) Avoid Async socket operations for systems that need to scale to large
> numbers.  Prefer Select I guess.
> 2) Reimplement the Async sockets to make sure they always use native
> operating system asynchronous facilities.
> I think you already said that in the 2.6 kernel, the Async Sockets use
> the posix aio interface.
> It seems like in linux 2.4 there is a means to get the kernel to send
> signals a socket is ready for IO:
> http://www.kegel.com/c10k.html#nb.sigio
> What would be the issues with doing a 2.4 implementation using the
> signals mechanism?

The native AIO interface support, apart from having some weird bugs and
being disabled now, cannot be used always. Why? aio_read/write do not
support passing extra sockets options.

I tested it under 2.4 and 2.6 kernel and it works (apart from the weird
bugs) fine.

I will reenable it once the bug is fixed.

Anyway, I suggest to use Select when you have such a big number of
sockets doing asynchronous operations.