HADOOP-7761 added functionality to compare byte arrays by treating them as arrays of 64-bit longs for performance. However HADOOP-11466 reverted this change for the SPARC architecture as it causes misaligned traps which causes performance to be worse rather than better.
Most platforms have a highly-optimised memcmp() libc function that uses processor-specific functionality to perform byte array comparison as quickly as is possible for the platform.
We have done some preliminary benchmarking on Solaris that suggests that, for reasonably-sized byte arrays, JNI code using memcmp() outperforms both of the current Java byte-size and long-size implementations on both SPARC and x86 . We are confirming the results and will repeat the same benchmark on Linux and report the results here for discussion.