RFR (M): 8022800: Use specific generations rather than generation iteration

[Bengt Rutisson]

Thanks Jon and Erik for reviews!

Here is an updated webrev that address some minor comments from Erik:
http://cr.openjdk.java.net/~brutisso/8022800/webrev.01/

Bengt

On 8/12/13 3:34 PM, Bengt Rutisson wrote:
>
> Hi everyone,
>
> Could I have a couple of reviews of this change?
>
> http://cr.openjdk.java.net/~brutisso/8022800/webrev.00/
>
> The interesting change is in genCollectedHeap.hpp, where I change the 
> methods prev_gen(), next_gen() and get_gen() to never return NULL. The 
> rest of the changes are ripple effects of this change.
>
> From the CR:
>
> The generations abstraction in the GC code was intended to be very 
> general. In practice we now always have exactly two generations - the 
> young and the old. This means that the GC code can be simplified quite 
> a bit.
>
> A first step is to change from iteration over generations to 
> explicitly specify which generation is needed. This makes the code 
> easier to follow and it also helps tools like Parfait to understand 
> the code better.
>
> This bug targets some simple clean-ups. A natural follow up of this is 
> probably to change the name of GenCollectedHeap to 
> TwoGenerationCollectedHeap (similar to the existing 
> TwoGenerationCollectorPolicy). But that will be handled separately.
>
> Thanks,
> Bengt
>