摘要:
Various technologies and techniques are disclosed for implementing retrying transactions in a transactional memory system. The system allows a transaction to execute a retry operation. The system registers for waits on every read in a read set of the retrying transaction. The retrying transaction waits for notification that something in the read set has changed. A transaction knows if notification is required in one of two ways. If the transactional memory word contained a waiters bit during write lock acquisition, then during release the transactional memory word is looked up in an object waiters map, and waiting transactions are signaled. If a writing transaction finds a global count of waiting transactions to be greater than zero after releasing write locks, a transaction waiters map is used to determine which waiting transactions need to be signaled. In each case, the write lock is released using a normal store operation.
摘要:
Various technologies and techniques are disclosed for handling exceptions in sequential statements that are executed in parallel. A transactional memory system is provided with a contention manager. The contention manager is responsible for managing exceptions that occur within statements that were designed to be executed in an original sequential order, and that were transformed into ordered transactions for speculative execution in parallel. The contention manager ensures that any exceptions that are thrown from one or more speculatively executed blocks while the statements are being executed speculatively in parallel are handled in the original sequential order.
摘要:
Various technologies and techniques are disclosed for supporting parallel nested transactions in a transactional memory system. Releasing a duplicate write lock for rollback is supported. During rollback processing of a parallel nested transaction, a write log entry is encountered that represents a write lock. If the write lock is a duplicate, a global lock is used to synchronize access to a global versioned write lock map. Optimistic read validation is supported. During validation, if a versioned write lock indicates a sibling conflict, consult information to determine if a parallel nested transaction should be doomed. Write lock acquisition is supported. Upon attempting to acquire a write lock for a parallel nested transaction, a transactional memory word is analyzed to determine if the write lock can be obtained. If the transactional memory word indicates a versioned write lock, retrieve a write log entry pointer from a global versioned write lock map.
摘要:
Various technologies and techniques are disclosed that provide software transactional protection of managed pointers. A software transactional memory system interacts with and/or includes a compiler. At compile time, the compiler determines that there are one or more reference arguments in one or more code segments being compiled whose source cannot be recovered. The compiler executes a procedure to select one or more appropriate techniques or combinations thereof for communicating the sources of the referenced variables to the called code segments to ensure the referenced variables can be recovered when needed. Some examples of these techniques include a fattened by-ref technique, a static fattening technique, a dynamic ByRefInfo type technique, and others. One or more combinations of these techniques can be used as appropriate.
摘要:
Various technologies and techniques are disclosed for supporting parallel nested transactions in a transactional memory system. Releasing a duplicate write lock for rollback is supported. During rollback processing of a parallel nested transaction, a write log entry is encountered that represents a write lock. If the write lock is a duplicate, a global lock is used to synchronize access to a global versioned write lock map. Optimistic read validation is supported. During validation, if a versioned write lock indicates a sibling conflict, consult information to determine if a parallel nested transaction should be doomed. Write lock acquisition is supported. Upon attempting to acquire a write lock for a parallel nested transaction, a transactional memory word is analyzed to determine if the write lock can be obtained. If the transactional memory word indicates a versioned write lock, retrieve a write log entry pointer from a global versioned write lock map.
摘要:
Various technologies and techniques are disclosed for supporting parallel nested transactions in a transactional memory system. Releasing a duplicate write lock for rollback is supported. During rollback processing of a parallel nested transaction, a write log entry is encountered that represents a write lock. If the write lock is a duplicate, a global lock is used to synchronize access to a global versioned write lock map. Optimistic read validation is supported. During validation, if a versioned write lock indicates a sibling conflict, consult information to determine if a parallel nested transaction should be doomed. Write lock acquisition is supported. Upon attempting to acquire a write lock for a parallel nested transaction, a transactional memory word is analyzed to determine if the write lock can be obtained. If the transactional memory word indicates a versioned write lock, retrieve a write log entry pointer from a global versioned write lock map.
摘要:
Various technologies and techniques are disclosed for supporting parallel nested transactions in a transactional memory system. Multiple closed nested transactions are created for a single parent transaction, and the closed nested transactions are executed concurrently as parallel nested transactions. Various techniques are used to ensure effects of the parallel nested transactions are hidden from other transactions outside the parent transaction until the parent transaction commits. For example, versioned write locks are used with parallel nested transactions. When a transactional memory word changes from a write lock to a versioned write lock, an entry is made in a global versioned write lock map to store a pointer to a write log entry that the versioned write lock replaced. When the versioned write lock is encountered during transaction processing, the global versioned write lock map is consulted to translate the versioned write lock to the pointer to the write log entry.
摘要:
Various technologies and techniques are disclosed for supporting parallel nested transactions in a transactional memory system. For example, pessimistic reads are supported. A pessimistic duplication detection data structure is created for a parallel nested transaction. An entry is made into the data structure for each pessimistic read in the parallel nested transaction. When committing the parallel nested transaction, new pessimistic read locks are passed to an immediate parent, and an entry is made into a separate pessimistic duplication detection data structure of the immediate parent with synchronization between sibling transactions. The pessimistic duplication detection data structures can also be used for upgrades from pessimistic reads to write locks. Retry operations are supported with parallel nested transactions. Write abort compensation maps can be used with parallel nested transactions to detect and handle falsely doomed parent transactions.
摘要:
Various technologies and techniques are disclosed for providing type stability techniques to enhance contention management. A reference counting mechanism is provided that enables transactions to safely examine states of other transactions. Contention management is facilitated using the reference counting mechanism. When a conflict is detected between two transactions, owning transaction information is obtained. A reference count of the owning transaction is incremented. The system ensures that the correct transaction was incremented. If the owning transaction is still a conflicting transaction, then a contention management decision is made to determine proper resolution. When the decision is made, the reference count on the owning transaction is decremented by the conflicting transaction. When each transaction completes, the reference counts it holds to itself is decremented. Data structures cannot be deallocated until their reference count is zero. Dedicated type-stable allocation pools can be reduced using an unstable attribute.
摘要:
Various technologies and techniques are disclosed for detecting falsely doomed parent transactions of nested children in transactional memory systems. When rolling back nested transactions, a release count is tracked each time that a write lock is released due to rollback for a given nested transaction. For example, a write abort compensation map can be used to track the release count for each nested transaction. The number of times the nested transactions releases a write lock is recorded in their respective write abort compensation map. The release counts can be used during a validation of a parent transaction to determine if a failed optimistic read is really valid. If an aggregated release count for the nested children transactions accounts for the difference in version numbers exactly, then the optimistic read is valid.