International Business Machines Corporation

IBM Canada Limited - IBM Canada Limitee

Charles Robert Gracie

Michael H Dawson

Graeme Johnson

Daniel J Heidinga

Aleksandar Micic

Graham Alan Chapman

Karl Michael Taylor

Michael Hilton Dawson

Andrew Russell Low

Peter Wiebe Burka

Peter Douglas Bain

Ryan Andrew Sciampacone

Prashanth K Nageshappa

Venkataraghavan Lakshminarayanachar

Joran S C Siu

Irwin D'Souza

Ashutosh Mehra

Filip Jeremic

Amar Devegowda

Dmitri Pivkine

A computerized operating system begins a garbage-collection operation by collecting a set of 'garbage' data objects to be deleted. Certain of these objects are identified, either by an embedded identifier or by an entry in a sensitive-objects data structure, as containing sensitive data. When the garbage collector moves or deletes a sensitive object during the garbage-collection procedure, the collector zeroes out any residual data left at the object's original location in memory or secondary storage. If the collector determines that the object no longer has any connection to other software entities, the collector zeroes out the storage locations of all identified instances of the object. The collector then updates the data structure to indicate the current location of sensitive objects that have been moved or copied, and deletes entries for zeroed out instances of deleted sensitive objects.

Operating system garbage-collection with integrated clearing of sensitive data

An approach for optimizing a copying of a data object in a concurrent copying garbage collection operation is provided. In an embodiment, a source copy of the data object to be copied as part of the garbage collection operation is identified. A copying of the source copy to a target location is initiated by a primary accessing thread. This initiating of the copying includes the creation of a temporary target object header for the target object in the target location that contains an indicator set to indicate that the copying is ongoing. As the copying is occurring, the execution of any other accessing threads that are attempting to use the data object are held for as long as the indicator indicates that the copying is ongoing. Once the copying has completed, the target object header is replaced with a copy of the source object header, resetting the indicator.

Copying and forwarding for concurrent copying garbage collection

An illustrative embodiment of a computer-implemented method for working set adjustment receives a request to use less heap memory than an original maximum forming a new maximum, and determines whether a garbage collection will move objects in response to the request. Responsive to a determination the garbage collection will move objects, add a first callback triggered by initiation of the garbage collection and invoking a handler for the first callback notifying a memory manager to free objects allocated by balloon. The first callback completes and the garbage collection starts. A handler for a second callback is invoked which notifies the memory manager to allocate balloon objects and frees backing memory to an operating system, the balloon objects consuming an amount of memory space equal to a remaining portion of memory necessary to return to the operating system. Completion of the second call back allows the garbage collection to proceed as usual.

Working set adjustment in a managed environment

An illustrative embodiment of a computer-implemented method for working set adjustment receives a request to use less heap memory than an original maximum forming a new maximum, and determines whether a garbage collection will move objects in response to the request. Responsive to a determination the garbage collection will move objects, add a first callback triggered by initiation of the garbage collection and invoking a handler for the first callback notifying a memory manager to free objects allocated by balloon. The first callback completes and the garbage collection starts. A handler for a second callback is invoked which notifies the memory manager to allocate balloon objects and frees backing memory to an operating system. Completion of the second call back allows the garbage collection to proceed as usual.

An illustrative embodiment of a computer-implemented method for estimating heap fragmentation in real time, models a runtime view of free heap memory, models a runtime view of heap allocation patterns for the heap memory and takes a snapshot of the heap memory. A batch allocator simulator is executed at a predetermined event and a remaining amount of memory unused in the simulation is identified as fragmented memory.

Allocation aware heap fragmentation metrics

Embodiments of the present invention disclose a method, system, and computer program product for a JNI object access system. A computer receives a JNI reference and obtains the pointer data and call site of the referenced object. The computer determines whether a record of the object and call site exist and, if not, the respective records are created. The computer applies a heuristic analysis of the object and call site in which it determines whether the object is larger than a threshold size, whether the object is part of a particular region of the heap, whether the call site is associated with a read-only or a read-write function, and whether the object or call site has caused more non-moving garbage collections than a threshold number. Based on the heuristic, the computer either copies the object data or pins the object and any non-moving garbage collections are recorded.

JNI object access

An unused free memory shortage relative to an adjusted heap maximum size associated with a memory heap of application memory is detected. The adjusted heap maximum size is set to a heap size smaller than a maximum heap allocation size. An increase to the adjusted heap maximum size that resolves the unused free memory shortage is calculated. The adjusted heap maximum size is increased by the calculated increase to the adjusted heap maximum size.

Out-of-memory avoidance in dynamic virtual machine memory adjustment

Out-of memory avoidance in dynamic virtual machine memory adjustment

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 computer-implemented process for write barrier elision during program execution receives a request to overwrite a reference, determines whether garbage collection is active and responsive to a determination that garbage collection is active, determines whether a reference object has been scanned. Responsive to a determination that the reference object has not been scanned set a mark bit for the reference object in a modified mark map, the reference object is scanned and a scan bit is set for the reference object in the modified mark map.

Write barrier elision for reference arrays

Garbage collection processes are automatically tuned on a system comprising a plurality of virtual machines running on a physical processing device with multiple physical processors. Tuning is implemented for each garbage collection process, by updating a load variable to reflect that a new garbage collection process has started, the load variable having a value that is based at least in part on a number of garbage collection processes that are currently running on the system. Tuning further comprises creating a number of garbage collection threads based at least in part on the current value of the load variable and/or number of processors, where the garbage collection threads are used to perform at least a portion of at least one phase of the new garbage collection process. Tuning further comprises re-updating the load variable to reflect completion of the new garbage collection process.

Garbage collection in a multiple virtual machine environment

A Java object is scan-missed during the mark phase of a garbage collection cycle. A list of any unscanned objects, comprising all objects of a particular object type, is created during a sweep phase of the garbage collection cycle. After the garbage collection cycle is completed, and the application resumes, for every PUTFIELD/GETFIELD operation on the object type that is part of a specific parent object, a comparison is made with the relevant information in the unscanned objects list. A scan-miss is identified by determining whether the current object being referenced by the application is a part of the unscanned object list that has been created during the sweep phase of the garbage collection cycle.

Growing community of inventors

Kanata, Canada

Charles Robert Gracie