[D-runtime] D Concurrent GC

[Steve Schveighoffer]

----- Original Message ----
> From: Sean Kelly <sean at invisibleduck.org>
> 
> On Sep 27, 2010, at 3:09 PM, Leandro Lucarella wrote:
> > 
> > Sean  Kelly, el 24 de septiembre a las 09:47 me escribiste:
> >
> >> I'll have to see what I've  changed in the GC since creating druntime
> >> as well.  Nothing  major I think though.
> > 
> > I think the array appending changes are  the bigger since the last time
> > I checked.
> 
> There's an APPENDABLE  flag now.  I'll check the diffs in the GC code to see if 
>there's anything  else.  Thanks for the  reply!

Basically, APPENDABLE is used to mark a memory block as being an appendable 
array.  This helps prevent accidental appending when the array runtime code 
hasn't been used.

It was pretty easy to add, I just copy-pasted some code that creates the bits.  
The toughest part really was to go through all the modules that define BlkAttr 
and add the APPENDABLE flag (unsure why this isn't done in one place...).

There are some other changes I made, particularly to extend.  Basically, the old 
extend would give up after adding one page if it was available.  I changed it to 
add as many pages as possible up to the upper limit request size.  This helps 
keep appending amortized because the array grows proportionately instead of one 
page at a time.

However, if your GC does not implement this, it's not a severe problem, it just 
won't perform quite as well when appending.

-Steve