Transaction Code Optimizations

Currently, I found the following problems (so far, last update 18/01, 17h30, fix in progress):

• the LocalTxInvocationContext is creating an empty map every time a new instance is created. It originates >10GB of data in 5min. It can use the Collections.emptyMap()

• TransactionCoordinator is creating LocalTxInvocationContext twice when commit. First, prepare() method creates LocalTxInvocationContext and if it is read only, it invokes commitInternal (that will create a new LocalTxInvocationContext). The same for commit() method when the transaction is one phase. commitInternal() can reuse the LocalTxInvocationContext since they are stateless (and they already have a reference for the LocalTransaction).

• Refactor LocalTxInvocationContext and RemoteTxInvocationContext

Results (for 5 min profiling):

• HashMap allocation reduced from 20.80GB to 3.76GB
• LocalTxInvocationContext allocation reduced from 13.80GB to 7.44GB