RFR: 8205676: ZGC: Remove TLAB allocations in relocation path

[Per Liden]

Thanks Stefan!

/Per

On 2018-06-27 15:18, Stefan Karlsson wrote:
> Looks good.
> 
> StefanK
> 
> On 2018-06-26 12:45, Per Liden wrote:
>> During Java-thread aided relocation, ZGC tries to use the TLAB to 
>> allocate the new object. However, this interacts badly with JEP 331: 
>> Low-Overhead Heap Profiling, as it distorts the profiling statistics. 
>> I propose we remove the use of the TALB in the relocation path, 
>> essentially changing a thread-local pointer bump to a uncontended 
>> CPU-local CAS.
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8205676
>> Webrev: http://cr.openjdk.java.net/~pliden/8205676/webrev.0
>>
>> Testing: Currently running benchmarks to verify that this has no 
>> unexpected performance hit.
>>
>> I've filed two follow up RFEs (also out for review now), to clean up 
>> some functions that are now unused:
>> https://bugs.openjdk.java.net/browse/JDK-8205678
>> https://bugs.openjdk.java.net/browse/JDK-8205679
>>
>> /Per