Managing memory in a computer system

Patent metadata

Field	Value
Publication number	US-10909029-B2
Application number	US-201916394047-A
Country	US
Kind code	B2
Filing date	Apr 25, 2019
Priority date	May 15, 2012
Publication date	Feb 2, 2021
Grant date	Feb 2, 2021

Abstract

Methods, computer program products, and systems for managing memory in a computer system in which memory locations in use at any given time are represented as a set of memory objects in a first object graph. The first object graph includes a system root object associated by references to each of the memory objects. A method includes creating a second root object for the memory to form a second object graph for the memory. The method also includes, in response to the dereferencing of a first object from the first object graph, associating the dereferenced first object with the second object graph so that the second object graph includes at least one dereferenced object.

First claim

What is claimed is:

1. A method for managing memory in a computer system, the method comprising:
identifying one or more candidate objects in a dereferenced object graph, the one or more candidate objects being connected objects in the dereferenced object graph that are not marked as being live;
extracting dead object data from the one or more candidate objects;
storing the extracted dead object data; and
removing, after extracting the dead object data from the one or more candidate objects, the one or more candidate objects from memory.

2. The method of claim 1 , the method further comprising:
traversing a system root object graph associated with a program; and
marking a set of objects in the system root object graph as live, the set of objects being objects that are connected to a system root object, wherein an object is considered live if it is in use by the program.

3. The method of claim 2 , wherein the identifying one or more candidate objects in the dereferenced object graph comprises:
traversing the dereferenced object graph to identify one or more dereferenced objects that are not marked as live.

4. The method of claim 3 , the method further comprising:
identifying one or more dereferenced objects in the dereferenced object graph that are marked as live;
identifying metadata objects associated with the one or more live dereferenced objects;
marking the metadata objects as live; and
returning, after removing the one or more candidate objects from memory, memory allocations of the one or more candidate objects to a heap.

5. The method of claim 4 , wherein the candidate objects do not include metadata objects, and wherein the metadata objects include dead information objects and field definition objects.

6. The method of claim 1 , wherein the dead object data for a candidate object includes an object identifier that identifies the candidate object, an identification of a parent object of the candidate object, and referencing field data that identifies a field in the parent object that referenced the candidate object.

7. The method of claim 1 , the method further comprising:
providing, by a memory manager, memory allocations from a first heap and a second heap, the first heap including storages for connected objects, the second heap including storage for a dead root object and metadata objects;
creating, in response to dereferencing an object in the first heap, a corresponding set of metadata objects in the second heap, the corresponding set of metadata objects including a cross-heap reference to the dereferenced object in the first heap.

8. A system for managing memory, the system comprising:
a memory, wherein memory locations in the memory that are in use at any given time are represented as a set of memory objects in a system root object graph, the system root object graph including a system root object associated by references to each of the memory objects; and
a processor configured to perform a method comprising:
identifying one or more candidate objects in a dereferenced object graph, the one or more candidate objects being connected objects in the dereferenced object graph that are not marked as being live;
extracting dead object data from the one or more candidate objects;
storing the extracted dead object data; and
removing, after extracting the dead object data from the one or more candidate objects, the one or more candidate objects from memory.

9. The system of claim 8 , the method further comprising:
traversing a system root object graph associated with a program; and
marking a set of objects in the system root object graph as live, the set of objects being objects that are connected to a system root object, wherein an object is considered live if it is in use by the program.

10. The system of claim 9 , wherein the identifying one or more candidate objects in the dereferenced object graph comprises:
traversing the dereferenced object graph to identify one or more dereferenced objects that are not marked as live.

11. The system of claim 10 , the method further comprising:
identifying one or more dereferenced objects in the dereferenced object graph that are marked as live;
identifying metadata objects associated with the one or more live dereferenced objects;
marking the metadata objects as live; and
returning, after removing the one or more candidate objects from memory, memory allocations of the one or more candidate objects to a heap.

12. The system of claim 11 , wherein the candidate objects do not include metadata objects, and wherein the metadata objects include dead information objects and field definition objects.

13. The system of claim 8 , wherein the dead object data for a candidate object includes an object identifier that identifies the candidate object, an identification of a parent object of the candidate object, and referencing field data that identifies a field in the parent object that referenced the candidate object.

14. The system of claim 8 , the method further comprising:
providing, by a memory manager, memory allocations from a first heap and a second heap, the first heap including storages for connected objects, the second heap including storage for a dead root object and metadata objects;
creating, in response to dereferencing an object in the first heap, a corresponding set of metadata objects in the second heap, the corresponding set of metadata objects including a cross-heap reference to the dereferenced object in the first heap.

15. A computer program product comprising a computer readable storage medium having program code embodied therewith, wherein the computer readable storage medium is not a transitory signal per se, the program code executable by a processor to cause the processor to perform a method comprising:
identifying one or more candidate objects in a dereferenced object graph, the one or more candidate objects being connected objects in the dereferenced object graph that are not marked as being live;
extracting dead object data from the one or more candidate objects;
storing the extracted dead object data; and
removing, after extracting the dead object data from the one or more candidate objects, the one or more candidate objects from memory.

16. The computer program product of claim 15 , the method further comprising:
traversing a system root object graph associated with a program; and
marking a set of objects in the system root object graph as live, the set of objects being objects that are connected to a system root object, wherein an object is considered live if it is in use by the program.

17. The computer program product of claim 16 , wherein the identifying one or more candidate objects in the dereferenced object graph comprises:
traversing the dereferenced object graph to identify one or more dereferenced objects that are not marked as live.

18. The computer program product of claim 17 , the method further comprising:
identifying one or more dereferenced objects in the dereferenced object graph that are marked as live;
identifying metadata objects associated with the one or more live dereferenced objects;
marking the metadata objects as live; and
returning, after removing the one or more candidate objects from memory, memory allocations of the one or more candidate objects to a heap.

19. The computer program product of claim 18 , wherein the candidate objects do not include metadata objects, and wherein the metadata objects include dead information objects and field definition objects.

2

Assignees

• IBM

Inventors

• Slattery Edward J

Classifications

• G06F12/0253 Primary

  Garbage collection, i.e. reclamation of unreferenced memory · CPC title

• G06F16/901

  Indexing; Data structures therefor; Storage structures (for retrieval from the web G06F16/951) · CPC title

• G06F12/00 Primary

  Accessing, addressing or allocating within memory systems or architectures (digital input from, or digital output to record carriers, e.g. to disk storage units, G06F3/06) · CPC title

• G06F2212/1044

  Space efficiency improvement · CPC title

• G06F12/023

  Free address space management · CPC title