System and method for persistent RAM disk

• US 7,594,068 B2
• Filed: 07/17/2007
• Issued: 09/22/2009
• Est. Priority Date: 10/31/2003
• Status: Expired due to Fees

• Current Assignee: Superspeed Software Incorporated
• Original Assignee: Superspeed Software Incorporated
• Inventors: Diehl, Shawn T.
• Primary Examiner(s): Thai; Tuan V.
• Application Number:
  US11/879,254
• Publication Number:
  US 20080022410A1
• Time in Patent Office: 798 Days
• Field of Search: 711/100, 711/104, 711/105, 711/154, 726/26
• US Class Current: 711/104
• CPC Class Codes: G06F 11/1417 Boot up procedures
• CPC Class Codes: G06F 11/1441 Resetting or repowering
• CPC Class Codes: G06F 9/4418 Suspend and resume; Hibernate and awake

Abstract

The contents of a RAM disk are copied to an image file in nonvolatile memory on power-down and copied back on reboot to provide an appearance of persistence. A locking method can use in-use tables to limit access to the same blocks of data in a RAM disk.

Claims

1. A method for protecting data from loss or corruption due to simultaneous access to a portion of memory by two different program threads, comprising:

executing a memory gating program that tracks running threads and their memory demands;

creating and managing an in-use table that includes information about which threads are using which portions of memory, and which threads are waiting to use the same portions of memory;

allowing a thread to access a given portion of memory if it is not in use by another thread as indicated by the in-use table;

preventing a thread from accessing the given portion of memory if it is in use by another thread as indicated by the in-use table; and

accessing the memory in blocks sufficiently small in size so as to reduce the number of conflicts over a given memory block and to reduce the number of threads kept waiting for access to the same memory block.

2. The method of claim 1, further comprising determining a sequence of dependency, whereby a first thread is kept waiting for a second thread that is using the portion of memory, the determining including administration by the memory gating program of a succession of rights to the portion of memory in an organized fashion.

3. The method of claim 1 wherein the memory blocks comprise sectors having a maximum size of about 512 bytes per sector.

4. The method of claim 1, wherein the memory gating program is executed on a multi-threaded processor.

5. The method of claim 1, wherein the memory gating program is executed on more than one processor.

6. A method for protecting data from loss or corruption due to simultaneous access to a portion of memory by two different program threads, comprising:

executing a memory gating program that tracks running threads and their memory demands;

managing an in-use table that includes information about which threads are using which portions of memory, and which threads are waiting to use the same portions of memory;

allowing a thread to access a given portion of memory if it is not in use by another thread as indicated by the in-use table;

preventing a thread from accessing the given portion of memory if it is in use by another thread as indicated by the in-use table; and

accessing the memory in blocks sufficiently small in size so as to reduce the number of conflicts over a given memory block and to reduce the number of threads kept waiting for access to the same memory block.

7. The method of claim 6, further comprising determining a sequence of dependency, whereby a first thread is kept waiting for a second thread that is using the portion of memory, the determining including administration by the memory gating program of a succession of rights to the portion of memory.

8. The method of claim 6, wherein the memory is a RAM disk.

9. The method of claim 8, wherein the method is executed while the RAM disk is being loaded to a system memory.

10. The method of claim 8, wherein the memory blocks comprise sectors having a maximum size of about 512 bytes per sector.

11. The method of claim 6, wherein the in-use table contains a linked list, and wherein entries of the linked list correspond to threads using the memory.

12. The method of claim 6, wherein preventing a thread from accessing uses a mutual exclusion object acquired by a thread using the given portion of the memory.

13. The method of claim 6, wherein the memory gating program uses a list of gate entry objects, each gate entry object representing a portion of the memory.

14. The method of claim 6, further comprising accessing the memory in blocks sufficiently small in size so as to reduce the number of conflicts over a given memory block and to reduce the number of threads kept waiting for access to the same memory block.

15. The method of claim 6, wherein the memory blocks comprise sectors having a maximum size of about 512 bytes per sector.

16. The method of claim 6, wherein the memory gating program is executed on a multi-threaded processor.

17. A method for protecting data from loss or corruption due to simultaneous access to a portion of memory by two different program threads, comprising:

executing a memory gating program that tracks running threads and their memory demands;

managing an in-use table that includes information about which threads are using which portions of memory, and which threads are waiting to use the same portions of memory;

allowing a thread to access a given portion of memory if it is not in use by another thread as indicated by the in-use table;

preventing a thread from accessing the given portion of memory if it is in use by another thread as indicated by the in-use table;

determining a sequence of dependency, whereby a first thread is kept waiting for a second thread that is using the portion of memory, the determining including administration by the memory gating program of a succession of rights to the portion of memory; and

wherein determining a sequence of dependency includes keeping a counter indicating the number of threads that are using the portion of memory and to which the first thread depends.

18. A method for protecting data from loss or corruption due to simultaneous access to a portion of memory by two different program threads, comprising:

executing a memory gating program that tracks running threads on a multi-threaded processor and the memory demands of the threads;

managing an in-use table that includes information about which threads are using which portions of memory, and which threads are waiting to use the same portions of memory;

allowing a thread to access a given portion of memory if it is not in use by another thread a indicated by the in-use table; and

preventing a thread from accessing the given portion of memory if it is in use by another thread as indicated by the in-use table.

19. The method of claim 18, further comprising determining a sequence of dependency, whereby a first thread is kept waiting for a second thread that is using the portion of memory, the determining including administration by the memory gating program of a succession of rights to the portion of memory.

20. The method of claim 18, wherein the memory is a RAM disk.

21. The method of claim 20, wherein the method is executed while the RAM disk is being loaded to a system memory.

22. The method of claim 18, wherein the in-use table contains a linked list, and wherein entries of the linked list correspond to threads using the memory.

23. The method of claim 18, wherein preventing a thread from accessing uses a mutual exclusion object acquired by a thread using the given portion of the memory.

24. The method of claim 18, wherein the memory gating program uses a list of gate entry objects, each gate entry object representing a portion of the memory.

25. The method of claim 18, wherein the memory blocks comprise sectors having a maximum size of about 512 bytes per sector.