International Business Machines Corporation

Younes Manton

Michael K Gschwind

Giles R Frazier

Brian William Thompto

Karl Michael Taylor

Christian Jacobi

Anthony Saporito

Chung-Lung K Shum

Dan F Greiner

Jonathan D Bradbury

Timothy John Slegel

Vijay Sundaresan

Andrew James Craik

Yi Zhang

Timothy J Siegel

Joran S C Siu

An approach is provided for optimizing reference counting. Responsive to receiving code representing a program by a just-in-time compiler, one or more processors in computing machinery supporting transactional memory identify regions of the code having respective sets of reference counting operations executed dynamically. Identifying the regions of the code uses an analysis of semantics of the code. The identified regions are enclosed in respective transactions. The code that was to perform atomic operations, including the reference counting operations in the identified regions, is transformed into new code that performs non-atomic operations that are variants of the atomic operations. Fallback code sequences are inserted into the transformed code. In a non-transactional manner and in response to detections of failures in respective transactions, the fallback code sequences execute original code sequences that were in the code prior to the transformation of the code. The original code sequences include respective multiple atomic operations.

Using hardware transactional memory to optimize reference counting

A method and apparatus for garbage collection is disclosed herein. The method includes performing a garbage collection process without pausing execution of a runtime environment. The method also includes executing a first CPU instruction to load a first pointer that points to a first location in a first region of memory, where the first region of memory is undergoing garbage collection. The method also includes moving a first object pointed to by the first pointer from the first location in memory to a second location in memory.

Multi-section garbage collection

A method and apparatus for garbage collection is disclosed herein. The method includes specifying a load-monitored region within a memory managed by a run-time environment, enabling a load-monitored event-based branch configured to occur responsive to executing a first type of CPU instruction to load a pointer that points to a first location in the load-monitored region, performing a garbage collection process in background without pausing executing in the run-time environment, executing a CPU instruction of the first type to load a pointer that points to the first location in the load-monitored region, and responsive to triggering a load-monitored event-based branch, moving an object pointed to by the pointer with a handler from the first location in memory to a second location in memory.

Multi-section garbage collection method

Determining whether to perform atomic or conventional reference counting is provided. A single bit of a reference count corresponding to a reference-counted resource is read to determine whether to atomic reference counting is to be performed. It is determined whether the single bit of the reference count is set. In response to determining that the single bit is set, an atomic operation for atomic maintenance of the reference count corresponding to the reference-counted resource is performed by adjusting the reference count by a value of two. In response to determining that the single bit is not set, a conventional adjustment operation is performed for maintenance of the reference count corresponding to the reference-counted resource.

Dynamic resource visibility tracking to avoid atomic reference counting

Transient mode for an application is toggled. Transient mode for an application executing in the computing environment is activated. Based on activating transient mode for the application, a plurality of memory accesses are processed as transient accesses. Based on processing the plurality of memory accesses, transient mode for the application is deactivated.

Toggling modal transient memory access state

The embodiments relate to a computer system, computer program product and method for managing a garbage collection process. Processing control is obtained based on execution of a load instruction and a determination that an object pointer to be loaded indicates a location within a selected portion of memory undergoing a garbage collection process. The determination includes identifying a base address and size of a first memory block subject to the garbage collection, and assigning a binary value to each first memory block section. An image of the load instruction is obtained and a pointer address is calculated from the image. It is determined whether the object pointer is to be modified. The object pointer is modified and stored in a selected location.

A garbage collection facility is provided for memory management within a computer. The facility implements, in part, grouping of infrequently accessed data units in a designated transient memory area, and includes designating an area of the memory as a transient memory area and an area as a conventional memory area, and counting, for each data unit in the transient or conventional memory areas a number of accesses to the data unit. The counting provides a respective access count for each data unit. For each data unit in the transient memory area or the conventional memory area, a determination is made whether the respective access count is below a transient threshold ascertained to separate frequently accessed data units and infrequently used data units. Data units with respective access counts below the transient threshold are grouped together as transient data units within the transient memory area.

Garbage collection facility grouping infrequently accessed data units in designated transient memory area

Apparatus for a garbage collection is disclosed herein. The apparatus includes a processor that includes a load-monitored region register. A memory stores program code, which, when executed on the processor performs an operation for garbage collection, the operation includes specifying a load-monitored region within a memory managed by a runtime environment; enabling a load-monitored event-based branch configured to occur responsive to executing a first type of CPU instruction to load a pointer that points to a first location in the load-monitored region; performing a garbage collection process in background without pausing executing in the runtime environment; executing a CPU instruction of the first type to load a pointer that points to the first location in the load-monitored region; responsive to triggering a load-monitored event-based branch, moving an object pointed to by the pointer with a handler from the first location in memory to a second location in memory.

The embodiments relate to a method for managing a garbage collection process. The method includes executing a garbage collection process on a memory block of user address space. A load instruction is run. Running the load instruction includes loading content of a storage location into a processor. The loaded content corresponds to a memory address. It is determined if the garbage collection process is being executed at the memory address. The load instruction is diverted to a process to move an object at the memory address to a location outside of the memory block in response to determining that the garbage collection process is being executed at the first memory address. The load instruction is continued in response to determining that the garbage collection process is not being executed at the memory address.

Method and apparatus for managing memory is disclosed herein. In one embodiment, the method includes specifying a first load-monitored region within a memory, configuring a performance monitor to count object pointer accessed events associated with the first load-monitored region, executing a CPU instruction to load a pointer that points to a first location in the memory, responsive to determining that the first location is within the first load-monitored region, triggering an object pointer accessed event, updating a count of object pointer accessed events in the performance monitor, and performing garbage collection on the first load-monitored region based on the count of object pointer accessed events.

Scheme for determining data object usage in a memory region

The embodiments relate to a computer system, computer program product and method for managing a garbage collection process. Processing control is obtained based on execution of a load instruction and a determination that an object pointer to be loaded indicates a location within a selected portion of memory undergoing a garbage collection process. The determination includes identifying a base address and size of a first memory block subject to the garbage collection, subdividing the first memory block into sections, assigning a binary value to each section, and determining if the first memory block corresponds to the enabled section. An image of the load instruction is obtained and a pointer address is calculated from the image. The object pointer is read and it is determined whether the object pointer is to be modified. The object pointer is modified and stored in a selected location.

A computer-implemented method for identification of cache memory transiency may include identifying, with a processor, a virtual memory address section having a virtual memory address, determining, via the processor, a classification of cache memory transiency of the virtual memory address section, and determining, with the processor, based on the classification of cache memory transiency, a cache exemption status.

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Toronto, Canada

Younes Manton