RFR: Use PLAB for evacuations instead of TLAB

[Zhengyu Gu]

Hi Roman,

On 05/09/2018 02:11 PM, Roman Kennke wrote:
> Need to move around some UseTLAB guards. The GCLABs are enabled
> regardless of UseTLAB or not. Do we want to guard this with a separate flag?
> 
> Diff:
> http://cr.openjdk.java.net/~rkennke/plab-gclab/webrev.01.diff/
> Full:
> http://cr.openjdk.java.net/~rkennke/plab-gclab/webrev.01/

ShenandoahBarrierSet.cpp L384:
   thread is passed in as JavaThread*, so this test is unnecessary, and 
"else" path can be eliminated.


ShenandoahHeap.cpp L1499
   Need scope block for
1499   ShenandoahGCPhase phase(ShenandoahPhaseTimings::make_parsable);
1500   make_tlabs_parsable(true);

or should just keep UseTLAB test here to avoid misleading timing info, 
in case of phase time > 0.


Thanks,

-Zhengyu

> 
> 
> Roman
>