RFR (XS): 8035815: Pad and cache-align the BiasedMappedArray

[Thomas Schatzl]

Hi all,

  can I have reviews for the following tiny change? It adds padding for
all BiasedMappedArray instances.

Instances of those are frequently used in hot loops (or are going to,
see JDK-8027553), so it seems a good idea to let them start on cache
line boundaries and pad the tail.

Webrev:
http://cr.openjdk.java.net/~tschatzl/8035815/webrev/

CR:
https://bugs.openjdk.java.net/browse/JDK-8036860

Testing:
jprt

Thanks,
Thomas