Review request: 8015486: PSScavenge::is_obj_in_young is unnecessarily slow with UseCompressedOops

[Stefan Karlsson]

On 5/30/13 9:38 PM, Jon Masamitsu wrote:
> Very nice change.  Looks good.

Thanks.

StefanK
>
> Jon
>
> On 5/30/13 2:14 AM, Stefan Karlsson wrote:
>> http://cr.openjdk.java.net/~stefank/8015486/webrev.00/
>>
>> 8015486: PSScavenge::is_obj_in_young is unnecessarily slow with 
>> UseCompressedOops
>> Summary: Compare compressed oops to a compressed young gen boundary 
>> instead of uncompressing the oops before doing the young gen boundary 
>> check.
>>
>> Instead of decompressing every single oop before checking against the 
>> young gen boundary, we could store a compressed young gen boundary 
>> and compare the compressed oops against that value. This will save 
>> both a null-check and the decompression code for all the visited oops.
>>
>> This give about 3% lower young GC times when running SPECjbb2005.
>>
>> StefanK
>