US 7,734,667 B2Granted

System and method for reducing memory leaks in virtual machine programs

AssigneeInternational Business Machines Corporation

InventorJohn M. Lake

Life of this patent

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Abstract

A system and method is provided for reducing memory leaks in virtual machine programs, such as those encountered in programs running in the Java Virtual Machine (JVM) environment. A compiler, such as a Java Just-In-Time (JIT) compiler, is used to identify the last use of an variable and, subsequent to the program statement where the last use occurs, insert a nullification statement. The nullification statement nullifies the variable so that it no longer references an object stored in a garbage collected heap. Variables in a program are identified in the activation records of the program. The nullification statement, when executed, severs the link between the program and the objects stored in the garbage-collected heap so that the program is no longer seen as a “root” for the object, often enabling the garbage collector to reclaim memory occupied by the object sooner.

Claims8

Dependent claims

An information handling system comprising:

one or more processors;
a memory accessible by the processors;
a middleware software application that runs on the operating system, the middleware software application including a garbage-collected heap;
and
a nullification tool for nullifying program references, the nullification tool comprising steps effective to:
read, by a just in time compiler, one or more variables included in one or more activation records included in the middleware software application, wherein the variables reference one or more objects, the objects stored in the garbage-collected heap;
identify, by the just in time compiler, a program statement in the middleware software application where a selected variable is last used;
insert, by the just in time compiler, a nullification statement after the identified program statement, the nullification statement adapted to nullify the selected variable;
write the activation records, the identified program statement, and the nullification statement to a resulting code file for the middleware software application;
execute the middleware software application;
during execution of the middleware software application, execute the nullification statement to nullify the selected variable;
and
after nullifying the selected variable, execute a garbage collection program to identify one of the objects that was previously referenced by the selected variable, and reclaim the memory occupied by the identified object.

10 more elements

A computer program product stored in a computer operable media, the computer operable media containing instructions for execution by a computer, which, when executed by the computer, cause the computer to implement a method for automatically nullifying variables in a middleware computer program, said method comprising:

reading, by a just in time compiler, one or more variables included in one or more activation records included in the middleware computer program, wherein the variables reference one or more objects, the objects stored in a garbage collected heap stored in a computer memory;
identifying, by the just in time compiler, a program statement in the middleware computer program where a selected variable is last used;
inserting, by the just in time compiler, a nullification statement after the identified program statement, the nullification statement adapted to nullify the selected variable;
writing the activation records, the identified program statement, and the nullification statement to a resulting code file for the middleware computer program;
executing the middleware computer program, wherein the executing further comprises:
executing the nullification statement to nullify the selected variable;
and
after nullifying the selected variable, executing a garbage collection program, wherein executing the garbage collection program comprises identifying one of the objects that was previously referenced by the selected variable, and reclaiming the memory occupied by the identified object.

5 more elements

Dependencies are inferred from the claim text.

Facts

Application: 11/938,413Filed 12 Nov 2007 · continuation
Priority: 2 Jul 2003
Published: US 2008/0065708 A113 Mar 2008
Granted: 8 Jun 2010
Term ends: Not estimatedThe source records don’t support an estimate.

Classification3 codes

G06F 12/0269
Garbage collection, i.e. reclamation of unreferenced memory: incremental or concurrent garbage collection, e.g. in real-time systems
G06F 9/45516
Abstract machines for program code execution, e.g. Java virtual machine [JVM], interpreters or emulators: runtime code conversion or optimisation
G06F
Computing and data processing

Family

Application10/612,802Parent of this continuation · filed 2 Jul 2003
US 2008/0065708 A1Pre-grant publication · published 13 Mar 2008
US 7,340,493 B2Parent of this continuation
US 2005/0004884 A1Published application
US 7,734,667 B2This patent

From the US filing history. Foreign family members aren’t listed.