Disable GC entirely

[Rainer Schuetze]

On 10.04.2013 08:26, Manu wrote:
> On 10 April 2013 16:14, Rainer Schuetze <r.sagitario at gmx.de> wrote:
>
>>
>>
>> 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.
>>
>
> It's all rather useless without some powerful tools for tracking down
> leaks, and unintended allocations though. There will surely be bugs with
> this idea, and finding them will be a nightmare.
>

It needs some kind of manual ownership handling that's more or less 
similar as what you do in C++ right now. IMO it allows to workaround 
some bad consequences due to the mere existence of the GC without giving 
up its benefits in other threads.

I don't expect a GC any time soon with pause times acceptable for real 
time tasks. I'd be happy if they were acceptable for standard 
interactive programs (hopefully the concurrent version can be ported to 
Windows aswell).