Computer memory conservation system

• US 6,064,811 A
• Filed: 06/17/1996
• Issued: 05/16/2000
• Est. Priority Date: 06/17/1996
• Status: Expired due to Term

• Current Assignee: McAfee, Inc. (McAfee, LLC)
• Original Assignee: Network Associates, Inc.
• Inventors: Spilo, Michael L, Daub, Jonathan A.
• Primary Examiner(s): Rinehart, Mark H.
• Application Number:
  US08/664,507
• Time in Patent Office: 1,429 Days
• Field of Search: 395/670, 395/674, 395/200.56, 395/651, 711/163, 711/170, 711/173
• US Class Current: 718/104
• CPC Class Codes: G06F 12/023 Free address space management

Abstract

A method for improving the availability of global DOS memory under Microsoft Windows has two primary aspects. First, upper memory blocks are linked to the global heap to increase the amount of global DOS memory available. Second, a reserved area of global DOS memory is maintained to prevent generic memory requests from being fulfilled therefrom. Valid requests for global DOS memory are intercepted to ensure that they are able to be allocated out of global DOS memory or the reserved area. Taken in conjunction, the two aspects of the invention substantially decrease the probability that unavailability of global DOS memory will result in application or system failure.

Claims

1. A method for preserving the availability of a limited region of memory in a computer system for use by a process which requires access to memory within the limited range comprising the steps of:

identifying a limited memory region for preservation, wherein the memory region is an unused part of memory;

preserving at least a portion of the limited memory region by marking the portion of the limited memory region as used;

detecting attempts to allocate from the limited range of memory;

determining whether a sufficient amount of free memory is available within the limited range to satisfy a detected allocation attempt; and

releasing, in response to a determination that a sufficient amount of free memory within the limited range of memory is not available, a sufficient amount of the preserved portion of memory to satisfy the allocation attempt.

2. The method of claim 1, wherein the marking step comprises allocating the quantity to a block.

3. The method of claim 1, further comprising the step of reissuing the attempt to allocate after the releasing step.

4. The method of claim 2, further comprising the steps of:

monitoring memory release functions to intercept a call to release memory belonging to the region;

upon intercepting such a call, determining the current size of the block; and

allocating a portion of the memory released by the call to the block if the current size is smaller than the initial size.

28. The method of claim 1, wherein the identifying and marking steps are at least performed during a boot process, and all but a portion of the quantity marked during the boot process is released upon completion of the boot process.

30. The method of claim 1, wherein said step of determining comprises the steps of:

intercepting the detected allocation attempt before it is processed; and

predicting the results of the allocation attempt.

31. The method of claim 1, wherein the step of determining comprises the steps of:

allowing the detected allocation attempt to be processed; and

determining whether the processed allocation attempt succeeded or failed.

32. The method of claim 31, further comprising the step of reissuing the attempt to allocate after the releasing step.

5. A method for increasing the availability of a limited memory area of memory in a computer system for use by a process which requires access to memory within the limited range, comprising the steps of:

identifying regions within a limited memory area that normally might remain unused; and

allocating at least some of the identified unused regions to form a reserved memory block; and

allowing virtual device drivers to claim memory from the limited memory area prior to the allocating step.

6. The method of claim 5 wherein the allocating step is performed by a virtual device driver loading later than other virtual device drivers.

7. The method of claim 6 wherein the allocating step is performed during the processing of the Init_-- Complete system broadcast.

8. The method of claim 5, further comprising the steps of:

detecting attempts to allocate from the limited memory area;

determining whether a sufficient amount of free memory is available within the limited range to satisfy a detected allocation attempt; and

releasing, in response to a determination that a sufficient amount of free memory within the limited range is not available, a sufficient amount of the preserved portion of the reserved memory block to satisfy the allocation attempt.

9. The method of claim 8, wherein the monitoring step is performed by intercepting calls to the Microsoft Windows VMM service _-- Allocate_-- Global_-- V86_-- Data_-- Area.

12. The method of claim 5, further comprising the step of linking the reserved memory into the global heap.

33. The method of claim 12, wherein the linking step comprises the steps of:

creating new global heap arena headers for the linear addresses corresponding to the reserved memory; and

walking the global heap arenas and linking the new arenas in sequence so as to maintain the increasing address order of the global heap.

10. A method for increasing the availability of a limited memory area, comprising the steps of:

identifying regions within the limited memory area that normally might remain unused;

allocating some or all of the regions to form a reserved memory block; and

allowing virtual device drivers to claim memory from the limited memory area prior to the allocating step;

wherein the limited memory area is the area between 640K and 1M on a PC-compatible computer.

11. The method of claim 10, wherein the regions are upper memory blocks.

13. A method for preserving the availability of a global DOS memory region under Microsoft Windows 3.1, comprising the steps of:

identifying a portion of the global DOS memory region for preservation;

marking a quantity of the identified region as used;

detecting attempts to allocate from the region;

upon a detection, analyzing one of actual or predicted results of the attempt to allocate; and

releasing a portion of the quantity to satisfy the attempt to allocate if the analysis indicates that there is insufficient memory for the allocation.

14. The method of claim 13, wherein the marking step comprises allocating the quantity to a block.

15. The method of claim 13, further comprising the step of reissuing the attempt to allocate after the releasing step.

16. The method of claim 14, further comprising the steps of:

monitoring memory release functions to intercept a call to release memory belonging to the region;

upon intercepting such a call, determining the current size of the block; and

allocating a portion of the memory released by the call to the block if the current size is smaller than the initial size.

26. The method of claim 16, wherein the functions include the GlobalDosFree function.

27. The method of claim 13, wherein the functions include the GlobalDosAlloc function.

17. A method for increasing the availability of global DOS memory under a Microsoft Windows operating system, which has upper memory available to virtual devices but not to Windows programs, comprising the steps of:

identifying areas within an upper memory region that normally might remain unused; and

allocating some or all of the areas to form a reserved memory block.

18. The method of claim 17, further comprising the step of allowing virtual device drivers to claim memory from the upper memory region prior to the allocating step.

19. The method of claim 18 wherein the allocating step is performed by a virtual device driver loading later than other virtual device drivers.

20. The method of claim 18 wherein the allocating step is performed during the processing of the Init_-- Complete system broadcast.

21. The method of claim 18, further comprising the steps of:

detecting attempts to allocate memory from the reserved memory block;

determining whether a sufficient amount of free memory is available within the limited range to satisfy a detected allocation attempt; and

releasing, in response to a determination that a sufficient amount of free memory within the limited range is not available, a sufficient portion of the reserved memory to satisfy the allocation attempt.

22. The method of claim 21, wherein the monitoring step is performed by intercepting calls to the Microsoft Windows VMM service _-- Allocate_-- Global_-- V86_-- Data_-- Area.

29. The method of claim 17, wherein the functions include the _-- Alloc_-- Global_-- V86_-- Data_-- Area.

23. A method for increasing the availability of global DOS memory under a Microsoft Windows operating system, which has an upper memory region available to virtual devices but not to Windows programs, comprising the steps of:

identifying areas within the upper memory region that normally might remain unused; and

allocating some or all of the areas to form a reserved memory block;

wherein the upper memory region is the area between 640K and 1M on a PC-compatible computer.

24. A method for increasing the availability of global DOS memory under a Microsoft Windows operating system, which has an upper memory region available to virtual devices but not to Windows programs, comprising the steps of:

identifying areas within the upper memory region that normally might remain unused;

allocating some or all of the areas to form a reserved memory block; and

linking the reserved memory into the global heap.

25. The method of claim 24, wherein the linking step comprises the steps of:

creating new global heap arena headers for the linear addresses corresponding to the reserved memory; and

walking the global heap arenas and linking the new arenas in sequence so as to maintain the increasing address order of the global heap.