1. A method of controlling a coalescing of outermost memory transactions, the coalescing causing committing of memory store data to memory for a first transaction to be done at transaction execution (TX) end of a second transaction, the method comprising: executing, by a processor, a run-time instrumentation program for monitoring and modifying an associated program having a plurality of transactions; and based, at least in part, on an analysis of gathered instrumentation information, dynamically modifying, by the processor, continued execution of the plurality of transactions by adding a coalescing instruction that controls, at least in part, a coalescing of one or more outermost transactions of the plurality of transactions.