Disable GC entirely

[Rainer Schuetze]

On 08.04.2013 05:12, Manu wrote:
> The GC really needs to be addressed in terms of performance; it can't stop
> the world for milliseconds at a time. I'd be happy to give it ~150us every
> 16ms, but NOT 2ms every 200ms.
> Alternatively, some urgency needs to be invested in tools to help
> programmers track accidental GC allocations.

I'm not sure if these have been proposed already in this long thread, 
but 2 very small patches could help a lot for realtime applications:

1. a thread local flag to disallow and detect GC allocations
2. a flag per thread to specify that the thread should not be paused by 
the GC during collections.

The latter would then put the responsibility on the programmer to ensure 
that no references are mutated in the non-pausing thread that don't 
exist anywhere else (to avoid the collection of objects used in the 
realtime thread). As anything in a realtime thread usually has to be 
pre-allocated anyway, that doesn't put a lot more constraints on it but 
to ensure having references to the pre-allocated data in other threads 
or global state.