RFR (S): 8079091: Remove dictionary NULL check on common path of BlockFreeList methods

[Jungwoo Ha]

The slower ones have higher error bars (error bars are 95% confidence
interval), and you can see that those are not statistically significant.
I'll reflect your suggestions and upload the new webrev.

On Wed, Apr 29, 2015 at 10:00 PM, Kim Barrett <kim.barrett at oracle.com>
wrote:

> On Apr 29, 2015, at 7:34 PM, Jungwoo Ha <jwha at google.com> wrote:
> >
> > BUG: https://bugs.openjdk.java.net/browse/JDK-8079091
> > Webrev: http://cr.openjdk.java.net/~jwha/8079091/webrev.00/
> >
> > Can someone sponsor this change?
> > I've seen ~3% speed up on DaCapo benchmarks. (results attached on the bug
> > page.)
>
> Wow!
>
> Hm.  There are a couple of benchmarks that are a little bit slower.  I
> don't know enough about that suite of benchmarks to know how important
> that might be.
>
> Since the dictionary is always being created at construction time, the
> null check in ~BlockFreelist is no longer needed either.
>
> It seems like a further improvement might be obtained by making the
> dictionary a direct member subobject of BlockFreelist, rather than
> allocating it as a separate object, thereby eliminating an
> indirection.
>
> Pre-existing: Why is there a cast in SpaceManager::block_freelists()?
>
> Pre-existing: I found the private BlockFreelist::dictionary() member
> function distracting rather than helpful, and would have preferred
> just using the private data member directly. But maybe that's just me.
> If _dictionary is changed to a subobject rather than a pointer, I'd
> suggest changing a bunch of "dictionary()->XXX" to "_dictionary.XXX".
>
>