RFR (XXS): 8134857: Inconsistency in maximum TLAB/PLAB size and humonguous object size

[Dmitry Fazunenko]

Hi Thomas,

The test you provided looks good.  I have some minor comments.

1) @requires vm.gc == null | vm.gc == "G1"
2) Please, use 4-space indent in the "runTest" and "main" methods.
3) Adding  a javadoc comment to the "runTest" method would be nice. It 
should tell what is tested.
Something like:
   Starts VM with the given G1 region size and PLAB size. It's expected 
that VM is successfully started
   only if PLAB size is less than or equal to ...

Thanks,
Dima


On 01.09.2015 19:07, Thomas Schatzl wrote:
> Hi all,
>
>    can I have another review about PLAB argument processing? G1 now only
> allows a maximum TLAB/PLAB size of heap region size / 2 - 1 words
> (because with JDK-8078555 the bounds are actually checked).
>
> This is wrong. Only heap region size / 2 + 1 objects are considered
> humongous (see G1CollectedHeap::is_humongous()). This bug disallows
> specification of Young- and OldPLABSizes of exactly heap region size /
> 2, which is inconvenient.
>
> Finding out the exact value for 2^(heap region size words)/2-1 for some
> testing is much more work than just specifying the "round" value.
>
> There is also no reason to disallow 2^(heap region size words) word
> sized T/PLABs.
>
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8134857
> Webrev:
> http://cr.openjdk.java.net/~tschatzl/8134857/webrev/
> Testing:
> jprt
>
> Thanks,
>    Thomas
>
>