Transactional block conflict resolution based on the determination of executing threads in parallel or in serial mode

A computer program product comprising a non-transitory computer readable storage medium having a computer readable program recorded thereon, wherein the computer readable program, when executed on a data processing system, causes the data processing system to:

• execute threads, in the data processing system, in a first conflict resolution mode of operation in which the threads execute conflicting transactional blocks speculatively;
• determine, for a transactional block, whether the first conflict resolution mode of operation is to be transitioned to a second conflict resolution mode of operation in which the threads accessing the conflicting transactional blocks are executed serially and non-speculatively;
• execute a thread that accesses the transactional block using the second conflict resolution mode of operation in response to the determination indicating that the first conflict resolution mode of operation is to be transitioned to the second conflict resolution mode of operation;
• and
• determine whether or not to transition the transactional block back from the second conflict resolution mode of operation to the first conflict resolution mode of operation, wherein the computer readable program to determine whether or not to transition the transactional block back from the second conflict resolution mode of operation to the first conflict resolution mode of operation further causes the data processing system to:
• maintain, in the transactional block profile entry, a transition counter identifying a number of accesses to transactional blocks having a same classification associated with the transactional block that have occurred since the transactional block was transitioned to the second conflict resolution mode of operation;
• determine whether the transition counter has a value that meets or exceeds a predetermined threshold;
• and
• transition the transactional block from the second conflict resolution mode of operation to the first conflict resolution mode of operation in response to the transition counter having the value that meets or exceeds the predetermined threshold.

An apparatus, comprising:

• a processor;
• and
• a memory coupled to the processor, wherein the memory comprises instructions which, when executed by the processor, cause the processor to:
• execute threads in a first conflict resolution mode of operation in which the threads execute conflicting transactional blocks speculatively;
• determine, for a transactional block, whether the first conflict resolution mode of operation is to be transitioned to a second conflict resolution mode of operation in which the threads accessing the conflicting transactional blocks are executed serially and non-speculatively;
• execute a thread that accesses the transactional block using the second conflict resolution mode of operation in response to the determination indicating that the first conflict resolution mode of operation is to be transitioned to the second conflict resolution mode of operation;
• and
• determine whether or not to transition the transactional block back from the second conflict resolution mode of operation to the first conflict resolution mode of operation, wherein the instructions to determine whether or not to transition the transactional block back from the second conflict resolution mode of operation to the first conflict resolution mode of operation further causes the processor to:
• maintain, in the transactional block profile entry, a transition counter identifying a number of accesses to transactional blocks having a same classification associated with the transactional block that have occurred since the transactional block was transitioned to the second conflict resolution mode of operation;
• determine whether the transition counter has a value that meets or exceeds a predetermined threshold;
• and
• transition the transactional block from the second conflict resolution mode of operation to the first conflict resolution mode of operation in response to the transition counter having the value that meets or exceeds the predetermined threshold.