International Business Machines Corporation

Erez Petrank

Elliot Karl Kolodner

Alain Charles Azagury

Zvi Yosef Yehudai

Katherine Barabash

Ethan Lewis

Yoav Ossia

A method for collecting garbage in a computing environment, the method including tracing root objects to their reachable objects in a population of objects, marking the traced objects, unmarking a marked card including any of the objects, tracing any marked object on the unmarked card to an unmarked referent object of the marked object, marking the unmarked referent object, and tracing the marked referent object to its reachable objects, concurrently with the operation of a mutator upon the population of objects within the computing environment, and, while no mutator operates upon the population of objects within the computing environment, marking the traced objects, tracing unmarked root object referents to their reachable objects, marking any of the objects, and designating any unmarked object in the population of objects as available for reallocation.

Mostly concurrent garbage collection

A method for memory management in execution of a program by a computer having a memory includes allocating respective portions of the memory to data objects using mutator threads of the program, whereby the objects are held in a heap created by the program. The data objects in the heap are traced so as to mark the data objects that are reachable at a given stage in the program. The computer loops over the mutator threads so as to verify for each of the mutator threads that every update to the allocated portions of the memory in progress by the mutator thread has been completed. The heap is then swept so as to free the memory that is allocated to the data objects that are not marked as reachable, for reallocation to new data objects.

Trace termination for on-the-fly garbage collection for weakly-consistent computer architecture

A method for performing garbage collection of memory objects in a memory heap, the method includes the steps of partitioning the heap into old and new generations. There follows the step of applying an on-the-fly garbage collection to memory objects in the young generation, whilst running simultaneously a program thread.

On-the-fly garbage collector

Improved method of replication-based garbage collection in a multiprocessing system comprising a plurality of processors, a memory divided into a current area (from-space) used by the processors during current program execution and a reserved area (to-space), and at least a garbage collector for performing, when necessary, a garbage collection consisting in flipping the roles of the current area and reserved area after all the live objects stored in current area have been copied into the reserved area and for reclaiming the current area after the flipping operation. Several program threads (mutators) are currently running in parallel and the garbage collector performs the garbage collection in parallel with the program threads, the flipping operation being performed after the program threads have been stopped and the garbage collection has been completed. The method comprises the steps of storing, during normal program execution, a record in a local buffer allocated to each program thread each time this one updates a memory location, and adding this local buffer when full to a global list of buffers using a first wait-free synchronization operation, and, during garbage collection, removing the local buffers one by one from the global list of buffers using a second wait-free synchronization operation, and looping over records in each removed local buffer and copying the updated memory locations into the reserved area until the global list is empty.

Method of replication-based garbage collection in a multiprocessor system

The present invention relates to a method of delaying space allocation for parallel copying garbage collection in a data processing system comprising a memory divided in a current area (from-space) used by at least a program thread during current program execution and reserve area (to-space), and wherein a copying garbage collection is run in parallel by several collector threads, the garbage collection consisting in stopping the program threads and flipping the roles of the current area and reserved area before copying into the reserved area the live objects stored in the current area. Such a method comprises the steps of checking ( ) by one collector thread the live objects of the current area to be copied in said reserved area, the live objects being referenced by a list of pointers; storing for each live object, a record into an allocation log, this record including at least the address of the object and its size; adding ( ) the object size to a total_size which is the accumulated size of all the checked objects for which a record has been stored in the allocation log; and copying ( ) all the checked objects into the reserved area when the value of total_size reaches a predetermined allocation bound.

Method of delaying space allocation for parallel copying garbage collection

A method for performing garbage collection of memory objects in a memory heap, the method includes the steps of partitioning the heap into old and new generations. There follows the step of applying an on-the-fly garbage collection to memory objects in the young generation, while running simultaneously a program thread.

A system for garbage collection of memory objects in a memory heap. The system includes a memory heap that is partitioned into few generations, each generation being partitioned into cards. The generations are associated with remembered sets and card markings data structure. Each card in the card markings data structure includes scan generation related data that represent generations for which the card has or has not to be scanned. The system further includes a processor communicating with the memory for scanning the cards according to the scan generation related data, and in response to identifying updated inter-generational pointers, the processor is capable of updating the remember set with the identified inter-generational pointers. The processor is further capable of updating the scan generation related data.

Method for combining card marking with remembered set for generational garbage collection with more than two generations

A system for garbage collection of memory objects in a memory heap. The system includes memory heap that is partitioned into respective old and young areas. The old area is partitioned into cars and is further associated with card markings and remembered sets data structures. The card markings include for each card, a card time stamp that represents the time that the card was updated. The car includes, for each car, a car time entry stamp that represents the time the remembered set of the car was updated. The system further includes a processor communicating with the memory, and being capable of identifying all cards that were updated later than the remembered set of a selected car. In response to the event, it performs identifying change in pointers that refer from the card to a memory object in the selected car and in response to identified change in pointers, updating the remembered set of the car with the identified pointers. The process is further capable of updating the car time stamp of the selected car.

Method for combining card marking with remembered sets for old area of a

In a computer application having a counter for setting first and second counter values in respect of first and second objects. The counter has a range of n possible values and being incremented or decremented in accordance with update criterion. The application taking an action according to whether the first counter value is larger or equal to the second counter value. A method for handling a courter overflow event whereby the counter is incremented beyond said range by executing the steps of: compacting the first and second counter values to m values (m&lt;n) so as to constitute first and second compacted counter values, such that if the first counter value id larger than or equal to the second counter value then the compacted first value is not smaller than the compacted second value, and setting the counter to a value from among n-m values within the specified range.

Growing community of inventors

Haifa, Israel

Erez Petrank