RFR (XS) 8230646: Epsilon does not extend TLABs to max size

[Aleksey Shipilev]

Bug:
  https://bugs.openjdk.java.net/browse/JDK-8230646

I was playing with performance benchmarks and noticed that Epsilon does not extend issued TLABs to
max tlab size, because of the simple overlook. TLAB allocation path asks GC about the max tlab size
currently available with unsafe_max_tlab_alloc(). But, in Epsilon code, there is discrepancy: the
caller interprets the returned value in bytes, while Epsilon code has the size in words. Every other
GC adjusts accordingly, Epsilon should too.

Fix:
  http://cr.openjdk.java.net/~shade/8230646/webrev.01/

Testing: gc/epsilon, jdk-submit

-- 
Thanks,
-Aleksey