Advice-based feedback for transactional execution
One embodiment provides a system that facilitates the execution of a transaction for a program in a hardware-supported transactional memory system. During operation, the system records a failure state of the transaction during execution of the transaction using hardware transactional memory mechanisms. Next, the system detects a transaction failure associated with the transaction. Finally, the system provides an advice state associated with the recorded failure state to the program to facilitate a response to the transaction failure by the program.
1. A computer-implemented method for facilitating the execution of a transaction for a program in a hardware-supported transactional memory system, comprising:
recording a failure state of the transaction using at least one failure bit in a set of failure bits in a checkpoint status (CPS) register in a register file during execution of the transaction;
detecting a transaction failure associated with the transaction;
calculating an advice state associated with the recorded failure state by using at least one of a number of cache misses encountered during the transaction, an address associated with the transaction failure, and a processor version associated with the hardware-supported transactional memory system; and
providing the advice state to the program to enable the program to facilitate a response to the transaction failure by the program.
2. The computer-implemented method of claim 1 , wherein the advice state is used by the program to:
retry the transaction;
perform a remedial action to address a source of the transaction failure; or
bypass the transaction.
3. The computer-implemented method of claim 2 , wherein bypassing the transaction failure involves executing an alternative code path provided by software transactional execution mechanisms.
4. The computer-implemented method of claim 2 , wherein bypassing the transaction failure involves executing a critical section while holding a lock.
5. The computer-implemented method of claim 1 , wherein the advice state is recorded in the CPS using at least one advice bit in a set of advice bits in the CPS.
6. The computer-implemented method of claim 5 , wherein the advice bits encode an advice code corresponding to:
no advice;
retry immediately;
retry after a delay;
retry with remediation; or
unlikely to succeed.
7. The computer-implemented method of claim 1 , wherein the advice state is calculated using the failure bits.
8. The computer-implemented method of claim 7 , wherein the advice state is further calculated using at least one of a program counter and a recent transaction attempt.
9. The method of claim 1 , wherein the register file in which the CPS is located is located in a processor that is executing the transaction.
10. A system for facilitating the execution of a transaction for a program in a hardware-supported transactional memory system, comprising:
a storage apparatus configured to record a failure state of the transaction using at least one failure bit in a set of failure bits in a checkpoint status (CPS) register in a register file during execution of the transaction; and
an execution mechanism within a processor, wherein the execution mechanism is configured to:
execute the transaction;
detect a transaction failure associated with the transaction;
calculate an advice state associated with the recorded failure state by using at least one of a number of cache misses encountered during the transaction, an address associated with the transaction failure, and a processor version associated with the hardware-supported transactional memory system; and
provide an advice state associated with the recorded failure state to the program to facilitate a response to the transaction failure by the program.
11. The system of claim 10 , wherein the advice state is used by the program to:
retry the transaction;
perform a remedial action to address a source of the transaction failure; or
bypass the transaction.
12. The system of claim 11 , wherein bypassing the transaction failure involves executing an alternative code path provided by software transactional execution mechanisms.
13. The system of claim 11 , wherein bypassing the transaction failure involves executing a critical section while holding a lock.
14. The system of claim 10 , wherein the advice state is recorded in the CPS using at least one advice bit in a set of advice bits in the CPS.
15. The system of claim 14 , wherein the advice bits encode an advice code corresponding to:
no advice;
retry immediately;
retry after a delay;
retry with remediation; or
unlikely to succeed.
16. The system of claim 10 , wherein the advice state is calculated using the failure bits.
17. The system of claim 16 , wherein the advice state is further calculated using at least one of a program counter and a recent transaction attempt.