Asynchronicity in D

[Jonas Drewsen]

On 31/03/11 23.20, Max Klyga wrote:
> On 2011-03-31 22:35:43 +0300, Jonas Drewsen said:
>
>> On 31/03/11 18.26, Andrei Alexandrescu wrote:
>>> snip
>>
>> I believe that we would need both the threaded async IO that you
>> describe but also a select based one. The thread based is important
>> e.g. in order to keep buffering incoming data while processing
>> elements in the range (the OS will only buffer the number of bytes
>> allowed by sysadmin). The select based is important in order to handle
>> _many_ connections at the same time (think D as the killer app for
>> websockets). As Robert mentions fibers would be nice to take into
>> consideration as well.
>>
>> What I also see as an unresolved issue is non-blocking handling in
>> http://erdani.com/d/phobos/std_stream2.html which fits in naturally
>> with this topic I think.
>>
>> I may very well agree mentoring if we get a solid proposal out of this.
>
> I'm very glad to hear this. Now my motivation doubled!
>>
>> /Jonas
>
> Any comments, if this proposal be more focused on asyncronous networking
> or should it address asyncronisity in Phobos in general?
>
> I researched a little about libev and libevent. Both seem to have some
> limitations on Windows platform.
>
> libev can only be used to deal with sockets on Windows and uses select,
> which limits libev to 64 file handles per thread.

Actually it seems the limit is OS version dependent and for NT it is 
32767 per process: http://support.microsoft.com/kb/111855

> libevent uses Windows overlaping I/O, but this thread[1] shows that
> current implementation has perfomance limitations.
> So one option may be to use either libev or libevent, and implement
> things on top of them.
> Another is to make a new implementation (from scratch, or reuse some
> code from Boost.ASIO[2]) using threads or fibers, or maybe both.
>
> 1. http://www.mail-archive.com/libevent-users@monkey.org/msg01730.html
> 2. http://www.boost.org/doc/libs/1_46_1/doc/html/boost_asio.html
>
>