On Thu, Apr 7, 2011 at 4:50 PM, Feng Hou <houfen@gmail.com> wrote:

On Wed, Apr 6, 2011 at 12:17 PM, Jason E. Aten <j.e.aten@gmail.com> wrote:

On Wed, Apr 6, 2011 at 8:13 AM, Marc Feeley <feeley@iro.umontreal.ca> wrote:

On 2011-04-03, at 11:04 PM, Feng Hou wrote:

> Hello everyone,
>
> Gambit has great concurrency support by green-thread and no-blocking I/O scheduling. However, they are only able to use one native thread on multicore hardware. I have noticed some wish list on wiki for multicore/multiprocessing concurrency support. I'm wondering whether 0MQ (http://www.zeromq.org/) can be used as substance for Gambit to build such capabilities.
>
> My thoughts are,
>
> -- Not just a FFI binding.
> -- Use it as message passing broker for multicore and distributed concurrency.
> -- Share nothing between the GVM thread and other in-process native threads (doing long CPU bound computation or blocking I/O).
> -- How to integrate 0MQ inter-thread transport to gambit green-thread scheduler without blocking it?
> -- Would it be possible to bind 0MQ inter-thread socket to gambit mailbox?
> -- How to integrate 0MQ I/O event poller with gambit I/O loop?
> -- Would it be better to expose 0MQ IPC/TCP/PGM socket types as Gambit Port objects?
>
> I realized they were way beyond my knowledge and skill level to implement (some may not even make sense, please correct me). Nevertheless, just want to see if others have similar thoughts or needs.
>
> Cheers,
> Feng Hou

I quickly read the 0MQ docs and it seems interesting.  I can give pointers to whoever wants to implement them into Gambit.

Marc

I'd be up for contributing on this.  ZMQ and Gambit together would be quite sweet on multicore and as the basis for very scalable distributed systems.

As an aside, the last missing piece would be using Google's Protocol Buffers (PB) for very efficient serialization.  I say this in reference to the comments in the Termite paper that the new serialization in Gambit was the only bottleneck that kept Termite from beating Erlang outright in all categories.  By the way, has the serialization situation improved? If so then perhaps PB is not necessary.  But PB would also give one really nice inter-language interoperability, since PB bindings are available from just about any language (sadly except Scheme; but perhaps the Common Lisp bindings could be ported without much trouble) at this point.

But back to ZMQ.   It would seem to be more general, as Feng suggests, to be able to use ZMQ from Gambit rather than just Termite.  I say this because if one could use ZMQ from Gambit, then there would be no need play elaborate games to get mutable state, (or variables that actually vary =) ; i.e. without needing to do the gen_server trick/(section 4.6 of the Termite paper workaround) when you actually need mutable variables. Unfortunately, I work with big enough data, that I really do need mutable variables.

So assuming that one wants to be able to use ZMQ in Gambit (which I would!), I'd be very glad to hear any advice on how to do that.

Jason

I'm glad to hear so much interest and help offered. I've been playing around a toy binding, and reading 0mq source. I'd like to share a few more concrete ideas.

0mq socket is a concurrent device, rather than an I/O device. It's very lightweight, essentially a concurrent in-memory queue. Hundreds of thousands to the same tcp end-point would only consume just one tcp connection. This seems a perfect fit to gambit green-thread model. Pulling socket send/recv in noblock mode loop is equivalent to spinning on memory CAS+fance of a pointer (this appears to be how zmq implements it). 0mq also provides a timer facility, but I believe it'd block gambit thread scheduler. Instead, gambit thread-yield!/thread-sleep! can be used for scheduling noblock send/recv pulling.  We can have thousands of green-threads pulling on thousands of 0mq sockets concurrently. This can be done fairly straightforward in user land. Ideally, it'd be nice to just write,

(write u8vector a-zmq-port)

(read u8vector a-zmq-port timeout: 10)

All looping/retry/yield/sleep can happen in gambit scheduler (need continuation magic?).  Even nicer would be able to bind sockets to thread mailboxes so messages are pumped into mailboxes on receiving automatically. So we can use Erlang/Termite style receive loop, which gambit already adopted for local thread message passing (Though I'm not too keen on sending messages to remote threads, i.e. erlang Pid model. IMO, It's too tightly coupled in distributed  environment, where 0mq subject-oriented message passing is better architecturally).

Hi Feng,

I'm glad to hear about your experiments and ideas.  Could elaborate on the last comment that I've quoted above, re "not too keen on sending messages to remote threads."   I think I must be misunderstanding something, because the whole point of ZMQ is to send messages to remote threads.  I'm also not clear what you mean by the terms subject-oriented message vs. too tightly coupled. Feel free to elaborate on these, if you can.

Thank you.

Best regards,

Jason