Easy & huge GC optimizations

[Etienne via Digitalmars-d]

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?