GARBAGE COLLECTION ABSENT USE OF SPECIAL INSTRUCTIONS

• US 20170004074A1
• Filed: 06/30/2015
• Published: 01/05/2017
• Est. Priority Date: 06/30/2015
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Frazier, Giles R., Gschwind, Michael K.
• Granted Patent: US 10,176,093 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 12/0253 Garbage collection, i.e. reclamation of unreferenced memory

Abstract

Garbage collection processing is facilitated. Based on execution of a load instruction and determining that an address of an object pointer to be loaded is located in a pointer storage area and the object pointer indicates a location within a selected portion of memory undergoing garbage collection, processing control is obtained by a handler executing within a processor of the computing environment. The handler obtains the object pointer from the pointer storage area, and determines whether the object pointer is to be modified. If the object pointer is to be modified, the handler modifies the object pointer. The handler may then store the modified object pointer in a selected location.

Claims

1. A computer program product for facilitating garbage collection within a computing environment, said computer program product comprising:

a computer readable storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method comprising;

obtaining processing control by a handler executing within a processor of the computing environment, the obtaining processing control being based on execution of a load instruction and a determination that an address of an object pointer to be loaded is located in a pointer storage area and the object pointer indicates a location within a selected portion of memory undergoing garbage collection;

based on obtaining processing control by the handler, obtaining by the handler from the pointer storage area the object pointer, the object pointer indicating a location of an object pointed to by the object pointer;

determining by the handler whether the object pointer is to be modified;

modifying by the handler, based on determining the object pointer is to be modified, the object pointer to provide a modified object pointer; and

storing, based on modifying the object pointer, the modified object pointer in a selected location.

2. The computer program product of claim 1, wherein the selected location is a location within the pointer storage area or a location specified by the load instruction.

3. The computer program product of claim 1, wherein the obtaining processing control is via an interrupt issued by processor hardware, the interrupt issued based on execution of the load instruction and determination that the address of the object pointer to be loaded is located in the pointer storage area and the object pointer indicates the location within the selected portion of memory undergoing garbage collection.

4. The computer program product of claim 1, wherein the selected portion of memory undergoing garbage collection is part of an object area that includes one or more other objects not undergoing garbage collection, and wherein one or more applications accessing the object area not undergoing garbage collection continue to process during garbage collection.

5. The computer program product of claim 1, wherein the method further comprises:

determining from execution of the load instruction the address of the object pointer;

comparing the address of the object pointer with data related to the pointer storage area to determine whether the address of the object pointer is located within the pointer storage area;

based on the comparing determining that the address of the object pointer is located within the pointer storage area, comparing the object pointer with information relating to the selected portion of memory to determine that the object pointer indicates the location within the selected portion of memory; and

providing control to the handler, based on determining the address of the object pointer is located within the pointer storage area and the object pointer indicates the location within the selected portion of memory.

6. The computer program product of claim 1, wherein the pointer storage area comprises a contiguous area of memory that includes a plurality of object pointer addresses.

7. The computer program product of claim 1, wherein the pointer storage area is indicated by one of a register or a location within memory.

8. The computer program product of claim 1, wherein the selected portion of memory is indicated by one of a register or a location within memory.

9. The computer program product of claim 8, wherein the register includes a base address of the selected portion of memory and a size of the selected portion of memory.

10. The computer program product of claim 1, wherein the load instruction includes one or more operation code fields to specify a load operation, a result field to be used to obtain the object pointer, and one or more other fields to be used in the load operation.

11. A computer system for facilitating garbage collection within a computing environment, said computer system comprising:

a memory; and

a processor in communications with the memory, wherein the computer system is configured to perform a method, said method comprising;

obtaining processing control by a handler executing within a processor of the computing environment, the obtaining processing control being based on execution of a load instruction and a determination that an address of an object pointer to be loaded is located in a pointer storage area and the object pointer indicates a location within a selected portion of memory undergoing garbage collection;

based on obtaining processing control by the handler, obtaining by the handler from the pointer storage area the object pointer, the object pointer indicating a location of an object pointed to by the object pointer;

determining by the handler whether the object pointer is to be modified;

modifying by the handler, based on determining the object pointer is to be modified, the object pointer to provide a modified object pointer; and

storing, based on modifying the object pointer, the modified object pointer in a selected location.

12. The computer system of claim 11, wherein the obtaining processing control is via an interrupt issued by processor hardware, the interrupt issued based on execution of the load instruction and determination that the address of the object pointer to be loaded is located in the pointer storage area and the object pointer indicates the location within the selected portion of memory undergoing garbage collection.

13. The computer system of claim 11, wherein the selected portion of memory undergoing garbage collection is part of an object area that includes one or more other objects not undergoing garbage collection, and wherein one or more applications accessing the object area not undergoing garbage collection continue to process during garbage collection.

14. The computer system of claim 11, wherein the method further comprises:

determining from execution of the load instruction the address of the object pointer;

comparing the address of the object pointer with data related to the pointer storage area to determine whether the address of the object pointer is located within the pointer storage area;

based on the comparing determining that the address of the object pointer is located within the pointer storage area, comparing the object pointer with information relating to the selected portion of memory to determine that the object pointer indicates the location within the selected portion of memory; and

providing control to the handler, based on determining the address of the object pointer is located within the pointer storage area and the object pointer indicates the location within the selected portion of memory.

15. The computer system of claim 11, wherein the selected location is a location within the pointer storage area or a location specified by the load instruction.

16-19. -19. (canceled)

20. A computer program product for facilitating processing within a computing environment, said computer program product comprising:

a computer readable storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method comprising;

obtaining processing control by a handler executing within a processor of the computing environment, the obtaining processing control being based on a determination that an object pointer to be accessed indicates a location within a specified memory area; and

based on obtaining processing control by the handler, taking action by the handler, the taking action comprising at least one of;

providing an alert;

preventing access to the specified memory area;

or modifying the object pointer and storing the modified object pointer.