RFR (XS) 8212005: Epsilon elastic TLAB sizing may cause misalignment

[Thomas Schatzl]

Hi Aleksey,

On Wed, 2018-10-10 at 16:43 +0200, Aleksey Shipilev wrote:
> Bug:
>   https://bugs.openjdk.java.net/browse/JDK-8212005
> 
> I thought we handle it properly, but we are not. This causes tier1_gc
> failures in x86_32 now.
> 
> Fix:
>   http://cr.openjdk.java.net/~shade/8212005/webrev.01/
> 
> Testing: Linux {x86_64, x86_32} gc/epsilon, jdk-submit (running)

  looks good.

One minor nit: the test seems to be very similar to
gc/TestObjectAlignment, maybe it can be changed slightly (e.g. not
bailing out immediately on 32 bit systems) for the same purpose.

Otoh we may not have Epsilon gc on rotation in our tests, so the test
might never be run with Epsilon explicitly.

Your call.

Thanks,
  Thomas