Locality problems caused by size based allocation?

[Jeff Sturm]

On Tue, 17 Dec 2002, Zack Weinberg wrote:
> > Got it.  But that puzzles me:  the Boehm collector allocates one size
> > of object per heap block, fitting your desription of size-based
> > allocation, yet there was a measureable improvement over ggc-page?
>
> The Boehm collector may choose better size buckets.  Our current
> choices are crap, and I have statistics to prove it.  (details will
> cheerfully be provided, but not now, because I'm not going to sit and
> wait for gnumeric to paint its window over this remote X11 session).

That makes sense.  Then it should be an interesting experiment to apply
Boehm's MERGE_SIZES algorithm to ggc-page.

> Also, I believe it uses a generational algorithm, which should knock
> down the large amount of time spent marking live objects.

Dan didn't say whether he had done GC_enable_incremental().  Besides,
Boehm's incremental/generational mode doesn't seem to help that much with
overall collector performance... I studied this quite a bit for Java
programs, and can forward details to anyone interested.

Jeff