Oracle International Corporation

Peter Benson

Harlan Sexton

David Unietis

Mark Jungerman

David Rosenberg

Robert H Lee

Scott Meyer

Jerry Schwarz

Techniques for memory management or analysis with conservative garbage collectors is provided. The native stack is analyzed during runtime to identify within frames references to objects in the heap space. An amount of memory is calculated that represents the memory implicated by the reference. A log can be generated that conveys the frame, location of the reference in the frame and amount of memory implicated by the reference.

Identification of false ambiguous roots in a stack conservative garbage collector

A method and software for managing class variables is described in which a variable-format container for static class variables is provided such that numeric class variables can be accessed directly while other kinds of class variables are accessed via a reference to an object.

Method of managing memory for class variables

A heap analyzer that processes a snapshot of the heap contained in a dump file is described. The heap analyzer tool can be configured to relocate the pointers in the dumped heap and allow developers to examine the heap in web browser by presenting markup for displaying a heap object in the browser and rendering pointers in the object as clickable links. When a link is selected, the pointer is followed to another object and markup is generated for rendering that object with its links. Furthermore, callbacks may be provided through an application programming interface (API) to allow developers to furnish their own code for analyzing and displaying their data structures.

Architecture for a scalable and user-extensible heap dump analysis tool

A method for scanning objects as for garbage collection is described that employ an ancillary data structure to describe the format of an object. Specifically, the data structure lists which parts of the object are references and how large each part of the object is. Scanning the object can efficiently occur by stepping through the object and the data structure in parallel.

Method for scanning discontiguous objects

A method and software for analyzing a heap is described, in which a snapshot is made of a heap, which can be later analyzed by an analysis tool when a program that had run out of memory is no longer running. In one embodiment, an object allocated by the program is accessed and copied into a file, and an address of the object allocated by the process is recorded in association with an offset in the file of the copy of the object. The copy of the object copied into the file has preferably the same size as the object allocated by the process. A heap analysis tool may then be run on the objects copied into the file.

Architecture for a scalable heap analysis tool

A method and software for managing pointers to external objects in a run-time environment are described in which eager external references are provided that allow session memory objects to point directly to certain call memory objects with machine pointers. The eager external references contain enough information to recreate the call memory objects in call memory at the beginning of the call and fix the session memory objects to point to the new locations of the recreated call memory objects.

Method for managing pointers to external objects in a run-time environment

Techniques are provided for accessing an instance of a recreatable object in a shorter-duration memory based on a reference located in a longer-duration memory, where the shorter-duration memory is associated with a call. One technique involves (1) locating, within the shorter-duration memory, a context structure associated with the call; (2) locating an XREF pointers array based on data cached within the context structure; (3) determining whether the XREF pointers array includes a pointer associated with the reference; and (4) if the XREF pointers array includes a pointer associated with the reference, then following the pointer to locate the instance within the shorter-duration memory. Another technique, which may be employed in addition to or instead of the first technique, involves: (1) when a class is activated, generating, within the shorter-duration memory, a class object associated with the class; (2) storing, within the class object, data for locating instances of recreatable objects associated with the class; (3) to dereference the reference, performing the steps of (a) determining that the reference is associated with the class; and (b) using the data within the class object to locate the instance of the recreatable object.

Accessing shorter-duration instances of activatable objects based on object references stored in longer-duration memory

A memory model for a run-time environment is disclosed that includes a process-specific area of memory where objects in call-specific area of memory and session-specific area of memory can be migrated to at the end of a database call. User-specific objects can be then migrated to the session-specific area of memory. In one embodiment, the process-specific area of memory can be saved in a disk file and used to hot start another instance of an application server.

Memory model for a run-time environment

A method and software for performing data migration is described in which a common data migration driver routine is provided to handle various and disparate kinds of migration operations in a conceptually unified manner. Differences between the migration operations are handled by variations in how the state of the data migration driver routine is initialized, including pointers to low-level routines. Furthermore, a table of actions can be used to direct the basic operation of object copying, external reference created, and object interning.

Method for performing data migration

An approach is provided for maintaining a write barrier during an assignment operation between a source object and a target object. A source tag is obtained from a first reference to the source object, and a target tag is obtained from a second reference to the target object. The source tag and the target tag are compared, such that if the source tag is in a predetermined relationship with the target tag, then a data structure (e.g., a remember table or exit table) associated with the write barrier is updated in accordance with the assignment operation. In one embodiment, the routine to update the data structure is dispatched from a function table based on a tag value in a header associated with the source object.

Write-barrier maintenance in a garbage collector

Efficient address calculation of invariant reference within a run-time environment is attained by a self-relative numeric reference format for run-time storage of references. A self-relative numeric reference format specifies the location of a reference object relative to a pointer to the referencing object as an integer value. The machine pointers and numeric references may be tagged, and a tag assignment is disclosed so that a self-relative numeric reference is generated from machine pointers by calculating a pointer difference, and a machine pointer to the referenced object is generated by adding the self-relative numeric reference to a machine pointer to the referencing object.

Address calculation of invariant references within a run-time environment

A method and apparatus for managing a run-time environment is provided for improving performance and scalability of networked computer systems. In one example of the invention, a method starts by loading a class file, the class file specifying a class that includes a static class variable and a static initializer to initialize the static class variable. The static initializer is then invoked to initialize the static class variable. The class and the initialized static class variable are then saved in a second class file. The second class file is then loaded into a shared memory, the second class file including the class and the initialized static class variable.

Method and apparatus for managing shared memory in a run-time environment

A static object system is provided to allow for code for implementing a run-time environment to be automatically generated that is compatible with a high-order systems programming language such as C. In particular, the meta-object system is static, object-oriented, and uses generic functions that can dispatch to an appropriate member function based on the types of one or more arguments. In one embodiment, the generated dispatch code uses a multi-way conditional branch.

Object type system for a run-time environment using generated high-order language instructions for generic functions

A method and software for managing memory are provided in which objects residing in session memory are formatted so the references contained in the objects are in a machine-independent format, namely, that the references are encoded numerically. An exit table is provided to handle references with session memory that refer to locations in call memory, in which each entry in the exit table is associated with a corresponding reference in session memory and contains a pointer to the location in call memory.

Memory management using migration for a run-time environment

Methods of memory management in a run-time environment are described. A mechanism is provided for registering a routine to deinitialize or deallocate a large object at the end of a call (e.g. by setting it to null to unreference the object), which prevents the large object from being migrated into session memory, e.g. when live objects are migrated at the end of the call. This routine is called after the finalization of garbage collected objects that may use the large object. In a subsequent call, the large object is checked before use to determine if the object is deinitialized and re-initialized if the large object was deinitialized.

Growing community of inventors

Boulder, UT, United States of America

Peter Benson