Method and system of memory management using stack walking

• US 20020029357A1
• Filed: 05/16/2001
• Published: 03/07/2002
• Est. Priority Date: 11/16/1998
• Status: Active Grant

• Current Assignee: RPX Corporation
• Original Assignee: Insignia Solutions Plc (America's Suppliers, Inc.)
• Inventors: Guthrie, Philippa Joy, Rautenbach, Keith, Darnell, Stephen, Plummer, Wayne, Sexton, Jeremy James, Kramskoy, Jeremy Paul, Charnell, William Thomas, Dias, Blaise Abel Alec, Wynn, Michael John, Thomas, Stephen Paul
• Granted Patent: US 6,766,513 B2
• Time in Patent Office: Days
• US Class Current: 714/9
• CPC Class Codes: G06F 11/3612 by runtime analysis performance monitoring G06F11/3466
• CPC Class Codes: G06F 12/0269 Incremental or concurrent garbage collection, e.g. in real-time systems G06F12/0261 takes precedence
• CPC Class Codes: G06F 2209/481 Exception handling
• CPC Class Codes: G06F 8/4442 Reducing the number of cache misses; Data prefetching cache prefetching G06F12/0862
• CPC Class Codes: G06F 8/445 Exploiting fine grain parallelism, i.e. parallelism at instruction level run-time instruction scheduling G06F9/3836
• CPC Class Codes: G06F 9/4484 Executing subprograms
• CPC Class Codes: G06F 9/449 Object-oriented method invocation or resolution
• CPC Class Codes: G06F 9/4491 Optimising based on receiver type
• CPC Class Codes: G06F 9/455 Emulation; Interpretation; Software simulation, e.g. virtualisation or emulation of application or operating system execution engines
• CPC Class Codes: G06F 9/45516 Runtime code conversion or optimisation
• CPC Class Codes: G06F 9/4812 by interrupt, e.g. masked
• CPC Class Codes: Y10S 707/99932 Access augmentation or optimizing
• CPC Class Codes: Y10S 707/99953 Recoverability
• CPC Class Codes: Y10S 707/99956 File allocation

Abstract

A method and system of memory management using stack walking. The method of managing memory in a computer system includes identifying compiled code to be deleted, examining the return addresses of the frames in the stack, determining whether any of the return address of the frames are in the range of addresses of the compiled code to be deleted, and if they are, then altering the contents of the frame determined to have a return address in the range of addresses of the compiled code to be deleted.

Claims

1. A method of managing memory in a computer system, the computer system having at least one stack with a plurality of frames and a thread associated with the stack, the method comprising:

identifying compiled code to be deleted, the compiled code having a range of addresses;

examining one of the plurality of frames of the stack, each frame having a return address;

determining whether the return address of the one of the plurality of frames is in the range of addresses of the compiled code; and

altering the contents of the one of the plurality of frames if the return address of the one of the plurality of the frames is in the range of addresses of the compiled code.

2. A method as claimed in claim 1, further comprising repeating the acts of examining, determining, and altering until all of the frames of the stack have been examined.

3. A method as claimed in claim 2, wherein the computer system includes a plurality of stacks, each stack associated with a thread and having a plurality of frames, the method further comprising repeating the acts of examining, determining, and altering until all threads have been examined.

4. A method as claimed in claim 2, further comprising deleting the compiled code.

5. A method as claimed in claim 1, further comprising inserting a write barrier in the compiled code.

6. A method as claimed in claim 1, further comprising adjusting frame fields to compensate for optimizations.

7. A method as claimed in claim 1, further comprising searching for a compiled version of non-native code that corresponds to the compiled code to be deleted.

8. A method as claimed in claim 1, further comprising interpreting a portion of non-native code that corresponds to the compiled code to be deleted.

9. A computer system comprising:

a control device;

a deleter coupled to the control device;

an interpreter coupled to the control device;

a compiler coupled to the control device; and

a stack walker coupled to the control device, the stack walker having access to glue code.

10. A computer system as claimed in claim 9, wherein the control device, deleter, interpreter, compiler, and stack walker are part of a virtual machine, and further comprising a host processor coupled to the virtual machine.

11. A computer system as claimed in claim 9, wherein the control device is operable to select compiled code to be deleted, the compiled code having a range of addresses.

12. A computer system as claimed in claim 11, wherein the system executes multiple threads, each thread having an associated stack with a plurality of frames, and wherein the stack walker is operable to pause threads and examine the frames in each stack to identify whether a return address of any frame falls with the range of addresses of the compiled code.

13. A computer system as claimed in claim 12, wherein the host processor is associated with a memory, and the associated stacks are located in the memory.

14. A computer system as claimed in claim 12, wherein the return address of any frame that falls within the range of addresses of the compiled code is modified to refer to the glue code.

15. A computer system as claimed in claim 14, wherein the glue code is arranged to check for the existence of a piece of compiled code.

16. A computer system as claimed in claim 14, wherein the glue code is arranged to transfer control to the interpreter.

17. A method of managing memory in a computer system, the computer system having a stack with a plurality of frames, each frame having a return address, the method comprising:

accessing the stack with a first thread one frame at a time;

accessing the stack with a second thread one frame at a time;

pausing the first thread only for the time it takes the second thread to access the current frame of the first thread;

identifying compiled code to be deleted, the compiled code having a range of addresses;

examining one of the plurality of frames of the stack;

determining whether the return address of the one of the plurality of frames is in the range of addresses of the compiled code; and

altering the contents of the one of the plurality of frames if the return address of the one of the plurality of the frames is in the range of addresses of the compiled code.