Easy & huge GC optimizations

[Rainer Schuetze via Digitalmars-d]

On 22.05.2014 21:04, Etienne wrote:
> On 2014-05-22 2:12 PM, Rainer Schuetze wrote:
>>
>> "NO_INTERIOR" is currently only used for the hash array used by
>> associative arrays. It is a bit dangerous to use as any pointer,slice or
>> register still operating on the array is ignored, so collecting it might
>> corrupt your memory.
>
> That's quite a relief, I was afraid of having to do it ;)
>
> I'm currently exploring the possibility of sampling the pointers during
> mark'ing to check if they're gone and using bayesian probabilities to
> decide whether or not to skip the pool.
>
> I explained it all here:
> https://github.com/D-Programming-Language/druntime/pull/797#issuecomment-43896016
>
>
> -- paste --
> Basically, when marking, you take 1 in X of the references and send them
> to a specific array that represents the pool they refer to. Then, next
> time you're going to collect you test them individually and if they're
> mostly there, you skip marking/free'ing for that particular pool during
> collection. You can force collection on certain pools every 1 in X
> collections to even out the average lifetime of the references.
>
> You're going to want to have a lower certainty of failure for big
> allocations, but basically you're using probabilities to avoid pushing a
> lot of useless load on the processor, especially when you're in a part
> of an application that's just allocating a lot (sampling will determine
> that the software is not in a state of data removal).
>
> http://en.wikipedia.org/wiki/Bayes_factor
>
> -- end paste --
>
> The bayes factor is merely there to choose the appropriate model that
> fits with the program. Bayesian inference would take care of deciding if
> a pool should end up being mark'ed. In other words, machine learning.
>
> Would you think it'd be a good optimization opportunity?

Hmm, I guess I don't get the idea. You cannot skip a pool based on some 
statistics, you might have references in there to anything. As a result 
you cannot collect anything.