Use MessagePort for direct connections between modules

[bemasc]

Currently, all inter-module messaging passes through the core environment. This effectively requires all message passing to acquire and release a single lock (i.e. the mainloop). This seems likely to create a performance bottleneck when transferring >1000 messages per second, as in uProxy. However, Web Workers are capable of connecting directly using a Transferable MessagePort, which would avoid the need to access the core environment when communicating between modules, and might alleviate this bottleneck.

[willscott]

firefox explicitly says they don't support this in web workers, so support
would have to be chrome only:
https://developer.mozilla.org/en-US/docs/Web/API/Transferable

On Wed, Apr 8, 2015 at 8:39 AM, Benjamin M. Schwartz <
[email protected]> wrote:

Currently, all inter-module messaging passes through the core environment.
This effectively requires all message passing to acquire and release a
single lock (i.e. the mainloop). This seems likely to create a performance
bottleneck when transferring >1000 messages per second, as in uProxy.
However, Web Workers are capable of connecting directly using a
Transferable MessagePort, which would avoid the need to access the core
environment when communicating between modules, and might alleviate this
bottleneck.

—
Reply to this email directly or view it on GitHub
#254.

[trevj]

I guess MessagePort is just one possible way of achieving this.

@willscott I seem to remember core.peerconnection had an optimisation for signalling channel message passing; is there any chance that would come in useful here?

[bemasc]

Looks to me like the Firefox way to do this might be SharedWorker.

[iislucas]

Also looks to me like they are planning to support it in the future, which would be cool.

@trevj The important thing freedom channels (that I think you're referring to) give us, at the moment, is that they support avoiding the child-parent freedom message bouncing which otherwise happens when a child module is passing a message to the core environment (without channels they bounce through the parent module - via freedom core env!).

Would be good to have a design doc on channels in freedom so we can review how they work and make sure the they have nice syntax for usage too; I imagine freedom channels could nicely abstract over the mechanism of inter-module communication (MessagePort, or freedom-core env bounced messages).

[bemasc]

The only reference I see to "freedom channels" is #48, which is a bit old and vague. It would definitely be nice to clear up some of these proposals.

[iislucas]

@soycode something fun to think about after firefox testing :)

[trevj]

It would also be a trivial piece of code if we could somehow just insert it in the core context.