International Business Machines Corporation

Globalfoundries Inc.

Maged M Michael

Michael K Gschwind

Valentina Salapura

Chung-Lung K Shum

Harold Wade Cain, Iii

Eric M Schwarz

Fadi Y Busaba

Timothy John Slegel

Dan F Greiner

Jonathan D Bradbury

Donald R DeSota

Robert Joersz

Douglas James Joseph

Ashwini K Nanda

Paul Edward McKenney

Marcel Mitran

Martin Ohmacht

Kai-Ting Amy Wang

Takuya Nakaike

Gheorghe Calin Cascaval

Vijay Anand Saraswat

Martin Vechev

Davis A Miller

Jing Ru Zheng

Colin B Blundell

Derek E Williams

Pratap Chandra Pattnaik

Thomas D Lovett

Kattamuri Ekanadham

Bruce Michael Gilbert

Michael C Wong

Yong-Jik Kim

Hung Qui Le

Naresh Nayar

Randal Craig Swanberg

Jose Eduardo Moreira

Eric N Lais

Bradly George Frey

Cathy May

Vikas Agarwal

Ali Ijaz Sheikh

Benjamin Herrenschmidt

Ankur Narang

Toshihiko Koju

Thomas Basil Smith, Iii

Monu Kedia

Priya Ashok Nagpurkar

Surya V Duggirala

Vijay Kumar Garg

Christoph Von Praun

A computer-implemented method includes the following operations. A transactional lock elision transaction including a critical section is executed. The critical section is processed. After the processing of the critical section and prior to a commit point in the transactional lock elision transaction, a status of a lock is checked. Responsive to a determination that a status of the lock is free, a result of the transactional lock elision transaction is committed.

Transactional lock elision with delayed lock checking

In a transactional memory environment including a first processor and one or more additional processors, a computer-implemented method includes identifying a memory location and sending a probe request from the first processor to the additional processors. The probe request includes the memory location. The computer implemented method further includes generating, by each additional processor, an indication including whether the memory location is in use for a transaction by the additional processor. The computer-implemented method further includes sending the indication from each additional processor to the first processor and proceeding, by the first processor, based on the indication.

Interprocessor memory status communication

A transaction within a computer program or computer application comprises program instructions performing multiple store operations that appear to run and complete as a single, atomic operation. The program instructions forming a current transaction comprise a transaction begin indicator, a plurality of instructions (e.g., store operations), and a transaction end indicator. A near-end of transaction indicator is triggered based on a speculative look ahead operation such that an interfering transaction requiring a halt operation may be delayed to allow the current transaction to end. A halt operation, also referred to as an abort operation, as used herein refers to an operation responsive to a condition where two transactions have been detected to interfere where at least one transaction must be aborted and the state of the processor is reset to the state at the beginning of the aborted transaction by performing a rollback.

Enabling end of transaction detection using speculative look ahead

A transactional memory system determines whether a hardware transaction can be salvaged. A processor of the transactional memory system begins execution of a transaction in a transactional memory environment. Based on detection that an amount of available resource for transactional execution is below a predetermined threshold level, the processor determines whether the transaction can be salvaged. Based on determining that the transaction can not be salvaged, the processor aborts the transaction. Based on determining the transaction can be salvaged, the processor performs a salvage operation, wherein the salvage operation comprises one or more of: determining that the transaction can be brought to a stable state without exceeding the amount of available resource for transactional execution, and bringing the transaction to a stable state; and determining that a resource can be made available, and making the resource available.

Determining if transactions that are about to run out of resources can be salvaged or need to be aborted

A transactional memory system dynamically predicts the resource requirements of hardware transactions. A processor of the transactional memory system predicts resource requirements of a first hardware transaction to be executed based on a resource hint, a type of hardware transaction that is associated with a given hardware transaction, and a previous execution of a prior hardware transaction that is associated with the type of hardware transaction. The processor allocates resources for the given hardware transaction based on the predicted resource requirements. The processor initiates execution of the first hardware transaction using at least a portion of the allocated resources.

Dynamic prediction of hardware transaction resource requirements

When executed, a transaction-hint instruction specifies a transaction-count-to-completion (CTC) value for a transaction. The CTC value indicates how far a transaction is from completion. The CTC may be a number of instructions to completion or an amount of time to completion. The CTC value is adjusted as the transaction progresses. When a disruptive event associated with inducing transactional aborts, such as an interrupt or a conflicting memory access, is identified while processing the transaction, processing of the disruptive event is deferred if the adjusted CTC value satisfies deferral criteria. If the adjusted CTC value does not satisfy deferral criteria, the transaction is aborted and the disruptive event is processed.

Hint instruction for managing transactional aborts in transactional memory computing environments

Techniques relate to handling outstanding cache miss prefetches. A processor pipeline recognizes that a prefetch cancelling instruction is being executed. In response to recognizing that the prefetch cancelling instruction is being executed, all outstanding prefetches are evaluated according to a criterion as set forth by the prefetch cancelling instruction in order to select qualified prefetches. In response to evaluating, a cache subsystem is communicated with to cause cancelling of the qualified prefetches that fit the criterion. In response to successful cancelling of the qualified prefetches, a local cache is prevented from being updated from the qualified prefetches.

Instruction to cancel outstanding cache prefetches

Embodiments relate to non-default instruction handling within a transaction. An aspect includes entering a transaction, the transaction comprising a first plurality of instructions and a second plurality of instructions, wherein a default manner of handling of instructions in the transaction is one of atomic and non-atomic. Another aspect includes encountering a non-default specification instruction in the transaction, wherein the non-default specification instruction comprises a single instruction that specifies the second plurality of instructions of the transaction for handling in a non-default manner comprising one of atomic and non-atomic, wherein the non-default manner is different from the default manner. Another aspect includes handling the first plurality of instructions in the default manner. Yet another aspect includes handling the second plurality of instructions in the non-default manner.

Non-default instruction handling within transaction

Discontiguous storage locations are prefetched by a prefetch instruction. Addresses of the discontiguous storage locations are provided by a list directly or indirectly specified by a parameter of the prefetch instruction, along with metadata and information about the list entries. Fetching of corresponding data blocks to cache lines is initiated. A processor may enter transactional execution mode and memory instructions of a program may be executed using the prefetched data blocks.

Prefetching of discontiguous storage locations in anticipation of transactional execution

Techniques relate to handling outstanding cache miss prefetches. A processor pipeline recognizes that a prefetch canceling instruction is being executed. In response to recognizing that the prefetch canceling instruction is being executed, all outstanding prefetches are evaluated according to a criterion as set forth by the prefetch canceling instruction in order to select qualified prefetches. In response to evaluating, a cache subsystem is communicated with to cause canceling of the qualified prefetches that fit the criterion. In response to successful canceling of the qualified prefetches, a local cache is prevented from being updated from the qualified prefetches.

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Danbury, CT, United States of America

Maged M Michael