International Business Machines Corporation

Peter Wiebe Burka

Ryan Andrew Sciampacone

Aleksandar Micic

Jeffrey Michael Disher

Daryl James Maier

Karl Michael Taylor

Graham Alan Chapman

Trent Gray-Donald

Nikola Grcevski

Andrew Russell Low

Peter Duncan Shipton

Elijah El-Haddad

Thomas Mark Walter Bottomley

Barry M Genova

Olivier P Thomann

Daniel J Heidinga

Graeme Johnson

Angela Lin

Peter Douglas Bain

Derek Bruce Inglis

Charles Robert Gracie

Zhong Liang Wang

Charles Brian Hall

John Duimovich

Patrick James Mueller

Gianni S Duimovich

T Mark W Bottomley

Filip Spacek

Ronald Servant

Ryan Andrew Sciampancone

Aleksander Micic

A technique for incrementally unloading classes using a region-based garbage collector is described. One aspect of such a technique includes maintaining a remembered set for a class set. The remembered set indicates whether instances of the class set are contained in one or more regions in memory, and in which regions the instances are contained. Upon performing an incremental garbage collection process for a subset of the regions in memory, the technique examines the remembered set to determine whether the class set includes instances in regions outside of the subset. If the remembered set indicates that the class set includes instances outside of the subset of regions, the technique identifies the class set as 'live.' This will preclude unloading the class set from the subset of regions.

Incremental class unloading in a region-based garbage collector

An illustrative embodiment of a computer-implemented process for managing a staging area creates the staging area for identified candidate cold objects, moves the identified candidate objects into the staging area, tracks application access to memory comprising the staging area and determines whether frequency of use information for a specific object exceeds a predetermined threshold. Responsive to a determination that the frequency of use information for the specific object exceeds a predetermined threshold, move the specific object into a regular area and determine whether a current time exceeds a predetermined threshold. Responsive to a determination that the current time exceeds a predetermined threshold, the computer-implemented process moves remaining objects from the staging area to a cold area.

Data staging area

An illustrative embodiment for serialization of pre-initialized objects receives a source code definition of a class, identifies a set of constants associated with the class in the source code to form a set of identified constants, creates a result object corresponding to each constant in the set of identified constants, and compiles the source code into a compiled form of the class. The illustrative embodiment further serializes each result object into a resource file associated with the class to form a set of serialized objects and replaces, in the compiled form of the class, each reference to a respective constant associated with the class from the set of identified constants with a corresponding dynamic instruction using a respective serialized object in the set of serialized objects.

Serialization of pre-initialized objects

A method for efficiently computing a hash value for a string is disclosed. In one embodiment, such a method includes receiving an original string comprising multiple characters. The method computes an original hash value for the original string. The method produces an updated string by performing at least one of the following updates on the original string: adding leading/trailing characters to the original string; removing leading/trailing characters from the original string, and modifying characters of the original string while preserving the length of the original string. The method then computes an updated hash value for the updated string by performing at least one operation on the original hash value, wherein the at least one operation takes into account the updates that were made to the original string. A corresponding apparatus and computer program product are also disclosed.

Efficient string hash computation

A method includes loading a software class containing class information for a lock state. The method includes allocating an instance of a software object derived from the software class, wherein the allocating includes allocating of a lock word as part of the instance of the software object. The lock word defines whether the object is locked by a thread of multiple threads. The method includes observing activity relative to the instance of the software object. The method includes responsive to observing the activity relative to the instance of the software object that indicates that the lock state of the instance of the software object is non-locking, removing the lock word from the instance of the software object.

Software object lock management using observations

An apparatus, process, and computer program product to merge types in an object-oriented program is disclosed herein. In one embodiment, a process may include analyzing a method within an object-oriented program to identify merge candidates. These merge candidates may then be recorded in a merge candidate list. The process may further include identifying at least two code paths in the method that merge into a single code path and that operate on different types. The types in these code paths may then be merged to a nearest common superclass listed in the merge candidate list. In selected embodiments, the types may be merged to the java.lang.Object class in the event the merge candidate list is empty.

Type merging technique to reduce class loading during Java verification

At least one region of a heap that includes memory allocations is analyzed, using age and occupancy criteria, across a number of local garbage collection cycles using a processor executing a region-based garbage collector. Based upon the analyzed age and occupancy criteria of the at least one region, at least one stable region in age and occupancy is identified among the at least one region of the heap across the number of local garbage collection cycles. Maintenance of a remembered set (RS) of external references into the at least one stable region is temporarily stopped for each identified stable region during at least one additional local garbage collection cycle.

Remembered set overhead reduction by deferred garbage collection of stable regions

Under the present invention, a hierarchical tree and corresponding Least Recently Used (LRU) list are provided. Both include a predetermined quantity of nodes that are associated with invariant data objects. The nodes of the tree typically include a set of pointers that indicate a position/arrangement of the associated invariant data objects in the LRU list, and a set of pointers that indicate a logical relationship among the other nodes.

Method, system and program product for interning invariant data objects in dynamic space constrained systems

A method to implement parallel, single-pass compaction in a garbage collector is described. In one embodiment, such a method includes conducting a planning phase for multiple regions to be compacted. During the planning phase, the method determines new locations for data entities in the multiple regions. The method then performs a move phase for the multiple regions to move the data entities to their new locations. During the move phase, the method initiates multiple compaction threads to move the data entities to their new locations. While executing, the compaction threads dynamically build a dependency graph of the regions being compacted. The dependency graph guarantees that no data entity is moved to its new location until all data entities that it overwrites have been moved to their new locations. A corresponding computer program product and apparatus are also disclosed herein.

Parallel, single-pass compaction in a region-based garbage collector

Embodiments include a method comprising loading a software class containing class information for a lock state. The method includes allocating an instance of a software object derived from the software class, wherein the allocating includes allocating of a lock word as part of the instance of the software object. The lock word defines whether the object is locked by a thread of multiple threads. The method includes observing activity relative to the instance of the software object. The method also includes, responsive to observing the activity relative to the instance of the software object that indicates that the lock state of the instance of the object is non-locking, removing the lock word from the instance of the object.

Remembered set overhead reduction by deferred garbage collections of stable regions

An illustrative embodiment of a computer-implemented process for compaction planning selects a source region from a set of regions to form a selected source region, initializes process data using information from the selected source region and responsive to a determination that a current destination is not NULL and not full, determines whether to atomically consume from a destination. Responsive to a determination to atomically consume from a destination, the computer-implemented process plans to evacuate into a consumed extent and updates the process data and responsive to a determination that the source region is empty, determines whether more work remains. Responsive to a determination that more work does not remain, the computer-implemented process generates a relocation table.

Compaction planning

An illustrative embodiment of a computer-implemented process for dynamic measurement and adaptation of a parallel copying garbage collector initializes values and data structures, receives an evacuate set, determines whether a new copy block is required and responsive to a determination that a new copy block is required, calculates a size of the new copy block. The computer-implemented process further selects a survivor region from a list of survivor regions to form a selected survivor region, places a lock on the selected survivor region, identifies a number of threads enqueued on the selected survivor region, responsive to a determination that a contention value exceeds a predetermined value, increases a size of the list of survivor regions, evacuates blocks to the selected survivor region and responsive to a determination that more evacuate blocks do not exist, terminates.

Dynamic measurement and adaptation of a copying garbage collector

An operating system or virtual machine of an information handling system (IHS) initializes a garbage collector to provide object memory compaction during application execution. The operating system or virtual machine performs move and fixup management within heap or object memory stores. The garbage collector identifies holes or unused portions of heap memory and moves one or more objects during compaction operations. After the garbage collector moves the object, a fixup cache tool fixes up the object pointers within the object. The fixup cache tool maintains a fixup cache that includes pointer information corresponding to the objects that the garbage collector moves. The fixup cache tool employs the pointer information within the fixup cache to update or otherwise fixup the objects within the heap that the garbage collector moves during compaction operations. The fixup cache may provide predictive pointer update information during fixup operations for each object move within the heap.

Growing community of inventors

Ottawa, Canada

Peter Wiebe Burka