Advanced Micro Devices Corporation

Stephan Diestelhorst

David S Christie

Martin Thomas Pohlack

Michael P Hohmuth

Jaewoong Chung

Luke Yen

Uwe Dannowski

Sebastian Martin Biemueller

Thomas Friebel

Rahmet U Karpuzcu

A processing core of a plurality of processing cores is configured to execute a speculative region of code a single atomic memory transaction with respect one or more others of the plurality of processing cores. In response to determining an abort condition for issued one of the plurality of program instructions and in response to determining that the issued program instruction is not part of a mispredicted execution path, the processing core is configured to abort an attempt to execute the speculative region of code.

Processor support for hardware transactional memory

In the described embodiments, entities in a computing device selectively write specified values to a lock variable in a local cache and one or more lower levels of a memory hierarchy to enable multiple entities to enable the concurrent execution of corresponding critical sections of program code that are protected by a same lock.

Concurrently executing critical sections in program code in a processor

A processing core of a plurality of processing cores is configured to execute a speculative region of code as a single atomic memory transaction with respect one or more others of the plurality of processing cores. In response to determining an abort condition for an issued one of the plurality of program instructions and in response to determining that the issued program instruction is not part of a mispredicted execution path, the processing core is configured to abort an attempt to execute the speculative region of code.

An apparatus, computer readable medium, and method of performing nested speculative regions are presented. The method includes responding to entering a speculative region by storing link information to an abort handler and responding to a commit command by removing link information from the abort handler. The method may include storing link information to the abort handler associated with the speculative region. When the speculative region is nested, the method may include storing link information to an abort handler associated with a previous speculative region. Removing link information may include removing link information from the abort handler associated with the corresponding speculative region. The method may include restoring link information to the abort handler associated with a previous speculative region. Responding to an abort command may include running the abort handler associated with the aborted speculative region. The method may include running the abort handler of each previous speculative region.

Nested speculative regions for a synchronization facility

A system and method for executing a transaction in a transactional memory system is disclosed. The system includes a processor of a plurality of processors coupled to shared memory, wherein the processor is configured to execute a section of code, including a plurality of memory access operations to the shared memory, as an atomic transaction relative to the execution of the plurality of processors. According to embodiments, the processor is configured to determine whether the memory access operations include any of a set of disallowed instructions, wherein the set includes one or more instructions that operate differently in a virtualized computing environment than in a native computing environment. If any of the memory access operations are ones of the disallowed instructions, then the processor aborts the transaction.

Virtualizable advanced synchronization facility

The described embodiments include a processor that handles operations during transactions. In these embodiments, the processor comprises one or more cores. During operation, at least one core is configured to monitor the acquisition of time stamps during transactions. The at least one core is further configured to prevent the acquisition of time stamps that meet predetermined conditions.

Accessing time stamps during transactions in a processor

A computing device initiates a transaction, corresponding to an application, which includes operations for accessing data stored in a shared memory and buffering alterations to the data as speculative alterations to the shared memory. The computing device detects a transaction abort scenario corresponding to the transaction and notifies the application regarding the transaction abort scenario. The computing device determines whether to abort the transaction based on instructions received from the application regarding the transaction abort scenario. When the transaction is to be aborted, the computing device restores the transaction to an operation prior to accessing the data stored in the shared memory and buffering alterations to the data as speculative alterations to the shared memory. When the transaction is not to be aborted, the computing device enables the transaction to continue.

Transactional memory conflict management

A method and apparatus for compiling software written to be executed on a microprocessor that supports at least one hardware transactional memory function is provided. A compiler that supports at least one software transactional memory function is adapted to include a runtime system that maps between the at least one software transactional memory function and the at least one hardware transactional memory instruction.

Compiler support technique for hardware transactional memory systems

A system and method for providing very large read-sets for hardware transactional memory with limited hardware support by monitoring meta data such as page table entries. The system and method include a Hardware-based Transactional Memory (HTM) mechanism that tracks meta-data such as page-table entries (PTE) rather than all the data itself. The HTM mechanism protects large regions of memory by providing conflict detection so that regions of memory can be located within a local read or write set.

Protecting large regions without operating-system support

A system and method are disclosed for increasing large region transaction throughput by making informed determinations whether to abort a thread from a first core or a thread from a second core when a conflict is detected between the threads. Such a system and method allow resolution of conflicts between a first thread and a second thread. In certain embodiments, the system and method allow a requester to detect a conflict under specific circumstances and make an intelligent decision whether to abort the first thread, enter a wait state to give the first thread an opportunity to complete execution or, if possible, abort the second thread.

TLB-walk controlled abort policy for hardware transactional memory

An apparatus and method is disclosed for a computer processor configured to access a memory shared by a plurality of processing cores and to execute a plurality of memory access operations in a transactional mode as a single atomic transaction and to suspend the transactional mode in response to determining an implicit suspend condition, such as a program control transfer. As part of executing the transaction, the processor marks data accessed by the speculative memory access operations as being speculative data. In response to determining a suspend condition (including by detecting a control transfer in an executing thread) the processor suspends the transactional mode of execution, which includes setting a suspend flag and suspending marking speculative data. If the processor later detects a resumption condition (e.g., a return control transfer corresponding to a return from the control transfer), the processor is configured to resume the marking of speculative data.

Automatic suspend atomic hardware transactional memory in response to detecting an implicit suspend condition and resume thereof

A system and method are disclosed wherein a processor of a plurality of processors coupled to shared memory, is configured to initiate execution of a section of code according to a first transactional mode of the processor. The processor is configured to execute a plurality of protected memory access operations to the shared memory within the section of code as a single atomic transaction with respect to the plurality of processors. The processor is further configured to initiate, within the section of code, execution of a subsection of the section of code according to a second transactional mode of the processor, wherein the first and second transactional modes are each associated with respective recovery actions that the processor is configured to perform in response to detecting an abort condition.

Processor with support for nested speculative sections with different transactional modes

A system and method are disclosed for allowing protection of larger areas than memory lines by monitoring accessed and dirty bits in page tables. More specifically, in some embodiments, a second associative structure with a different granularity is provided to filter out a large percentage of false positives. By providing the associative structure with sufficient size, the structure exactly specifies a region in which conflicting cache lines lie. If entries within this region are evicted from the structure, enabling the tracking for the entire index filters out a substantial number of false positives (depending on a granularity and a number of indices present). In some embodiments, this associative structure is similar to a translation look aside buffer (TLB) with 4 k, 2M entries.

Protecting large objects within an advanced synchronization facility

A method and apparatus are disclosed for implementing early release of speculatively read data in a hardware transactional memory system. A processing core comprises a hardware transactional memory system configured to receive an early release indication for a specified word of a group of words in a read set of an active transaction. The early release indication comprises a request to remove the specified word from the read set. In response to the early release request, the processing core removes the group of words from the read set only after determining that no word in the group other than the specified word has been speculatively read during the active transaction.

Preventing unintended loss of transactional data in hardware transactional memory systems

A computer-implemented method and article of manufacture is disclosed for enabling computer programs utilizing hardware transactional memory to safely interact with code utilizing traditional locks. A thread executing on a processor of a plurality of processors in a shared-memory system may initiate transactional execution of a section of code, which includes a plurality of access operations to the shared-memory, including one or more to locations protected by a lock. Before executing any operations accessing the location associated with the lock, the thread reads the value of the lock as part of the transaction, and only proceeds if the lock is not held. If the lock is acquired by another thread during transactional execution, the processor detects this acquisition, aborts the transaction, and attempts to re-execute it.

Growing community of inventors

Dresden, Germany

Stephan Diestelhorst