Lazy stack memory allocation in systems with virtual memory

• US 20050198464A1
• Filed: 03/03/2005
• Published: 09/08/2005
• Est. Priority Date: 03/04/2004
• Status: Abandoned Application

• Current Assignee: Sun Microsystems Incorporated (Oracle Corporation)
• Original Assignee: SavaJe Technologies, Inc. (Oracle Corporation)
• Inventors: Sokolov, Stepan
• Application Number:
  US11/071,868
• Publication Number:
  US 20050198464A1
• Time in Patent Office: Days
• US Class Current: 711/203
• CPC Class Codes: G06F 12/10 Address translation
• CPC Class Codes: G06F 12/145 the protection being virtual, e.g. for virtual blocks or segments before a translation mechanism
• CPC Class Codes: G06F 2212/451 Stack data
• CPC Class Codes: G06F 2212/657 Virtual address space management

Abstract

A method for mapping of logical memory regions (usually referred to as pages) of application addressable contiguous memory space to non-contiguous pages of the physical memory is provided. Each thread in an application is allocated a substantially larger amount of virtual memory, than will typically be used by the thread. Initially only the page at the top of the stack is mapped to a physical page. Later, as the stack expands, more pages of virtual memory are mapped to physical pages, up to the limit of the allocated amount. At the end opposite to the top of the stack, the page is marked as inaccessible, to allow reporting of a stack overflow condition.

Claims

1. A computer implemented method for allocating memory for use as stack memory comprising the steps of:

allocating a contiguous block of virtual memory for the stack memory, the size of the allocated block being substantially larger than necessary for the stack memory;

mapping a virtual page at the top of the allocated block to a first physical page of physical memory; and

upon detecting an access to a next virtual page of the allocated block, mapping the next virtual page to a second physical page of the physical memory.

2. The method of claim 1, further comprising:

identifying the page at the bottom of the allocated block as inaccessible to allow detection of a stack overflow condition.

3. The method of claim 1, wherein the stack memory is allocated for use by a thread.

4. The method of claim 3, wherein the thread is an application thread.

5. The method of claim 1, wherein the allocated block of memory is 64 KB and the physical page of memory is 4 KB.

6. The method of claim 3, wherein the thread is a kernel thread.

7. The method of claim 4, wherein the application thread is for a JAVA application.

8. The method of claim 1, wherein the second physical page is not contiguous with the first physical page.

9. A computer apparatus for allocating memory for use as stack memory comprising:

a contiguous block of virtual memory allocated for stack memory and having a size substantially larger than necessary for stack memory; and

a mapping assembly for (i) mapping a virtual page at the top of the allocated block to a first physical page of physical memory and for (ii) upon detecting access to a next virtual page of the allocated block, mapping the next virtual page to a second physical page of the physical memory.

10. The apparatus of claim 9 further comprising:

an identifier for identifying the page at the bottom of the allocated block as inaccessible to allow detection of a stack overflow condition.

11. The apparatus of claim 9, wherein the stack memory is allocated for use by a thread.

12. The apparatus of claim 11, wherein the thread is an application thread.

13. The apparatus of claim 9, wherein the allocated block of memory is 64 KB and the physical page of memory is 4 KB.

14. The apparatus of claim 11, wherein the thread is a kernel thread.

15. The apparatus of claim 12, wherein the application thread is for a JAVA application.

16. The apparatus of claim 9, wherein the second physical page is not contiguous with the first physical page.

17. A computer program product for allocating memory for use as stack memory, the computer program product comprising a computer usable medium having computer readable program code thereon, including program code which:

allocates a contiguous block of virtual memory for the stack memory, the size of the allocated block being substantially larger than necessary for the stack memory;

maps a virtual page at the top of the allocated block to a first physical page of physical memory; and

upon detecting an access to a next virtual page of the allocated block, maps the next virtual page to a second physical page of the physical memory.

18. A computer apparatus for allocating memory for use as stack memory comprising:

means for allocating a contiguous block of virtual memory for the stack memory, the size of the allocated block bring substantially larger than necessary for the stack memory; and

means for mapping a virtual page at the top of the allocated block to a first physical page of physical memory and upon detecting an access to a next virtual page of the allocated block, mapping the next virtual page to a second physical page of the physical memory.