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

[Jungwoo Ha]

http://cr.openjdk.java.net/~jwha/8079091/webrev.01

PTAL.

On Wed, Apr 29, 2015 at 10:22 PM, Jungwoo Ha <jwha at google.com> wrote:

> 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".
>>
>>
>