RFR(xs): 8199656: Make slow metaspace verifications switchable in debug builds

[coleen.phillimore at oracle.com]

This looks good.  I think it's useful to have a VerifyMetaspace develop 
flag, since you are currently making improvements to metaspace.   More 
things might go under this flag also.
thanks,
Coleen

On 3/15/18 3:09 AM, Thomas Stüfe wrote:
> Hi all,
>
> may I please have reviews for this small rfe:
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8199656
> webrev:
> http://cr.openjdk.java.net/~stuefe/webrevs/8199656-verifymetaspace-switch/webrev.00/webrev/
>
> We have a number of useful metaspace verifications which are all switched
> off via a const bool in code. This change makes these verifications
> switchable.
>
> Note: the switch is develop because all the verifications are ASSERT only,
> so it makes no sense to make it the switch diagnostic. If we want the tests
> in product builds too, we need to revise the test code.
>
> For the effect this has,
> try ./hotspot/variant-server/libjvm/gtest/gtestLauncher.exe
> -XX:-VerifyMetaspace -jdk:./images/jdk/
> --gtest_filter=MetaspaceAllocationTest*. With verifications, runtime almost
> triples in fastdebug.
>
> Thanks and Kind Regards, Thomas