Cooperative mechanism for efficient application memory allocation

• US 8,321,638 B2
• Filed: 03/06/2009
• Issued: 11/27/2012
• Est. Priority Date: 11/21/2005
• Status: Active Grant

• Current Assignee: Red Hat, Inc. (International Business Machines Corporation)
• Original Assignee: Red Hat, Inc. (International Business Machines Corporation)
• Inventors: van Riel, Henri Han, van de Ven, Adriaan DM
• Primary Examiner(s): KROFCHECK, MICHAEL C
• Application Number:
  US12/399,456
• Publication Number:
  US 20090172337A1
• Time in Patent Office: 1,362 Days
• Field of Search: None
• US Class Current: 711/154
• CPC Class Codes: G06F 12/023 Free address space management
• CPC Class Codes: G06F 12/08 in hierarchically structured memory systems, e.g. virtual memory systems
• CPC Class Codes: G06F 12/12 Replacement control
• CPC Class Codes: G06F 12/14 Protection against unauthorised use of memory or access to memory

Abstract

System, method and computer program product for allocating physical memory to processes. The method includes enabling a kernel to free memory in a physical memory space corresponding to arbitrarily sized memory allocations released by processes or applications in a virtual memory space. After freeing the memory, the system determines whether freed physical memory in the physical memory space spans one or more fixed size memory units (e.g., page frames). The method further includes designating a status of the one or more page frames as available for reuse; the freed page frames marked as available for reuse being available for backing a new process without requiring the kernel to delete data included in the freed memory released by the process. The kernel may organize pages marked as available for reuse in one or more local “pools” that is organized according to a variety of schemes which provide system efficiencies in that the kernel can eliminate the need for deleting of old data in those page frames without compromising data security.

Claims

1. A method, implemented by a processor, for allocating memory comprising:

denoting a freed memory unit of a physical memory as available for reuse, without altering process data in the freed memory unit;

receiving a request, associated with a process, for a memory allocation from the physical memory;

determining, by the processor in response to the request, whether the process data contained in the freed memory unit is disclosable to the process associated with the request; and

allocating, by the processor, the freed memory unit to the process, if the determining indicates that the process data is disclosable to the process;

or

allocating, by the processor, a memory unit other than the freed memory unit to the process, if the determining indicates that the process data is not disclosable to the process.

2. The method for allocating memory of claim 1, wherein determining comprises:

determining that the process data is disclosable to the process when the process data was previously stored by the process in the freed memory unit.

3. The method for allocating memory of claim 1, wherein determining comprises:

determining that the process data is disclosable to the process when a user associated with the process is the user associated with a second process that previously stored the process data in the freed memory unit.

4. The method for allocating memory of claim 1, wherein determining comprises:

determining that the process data is disclosable to the process when a security context associated with the process is compatible with the security context associated with a second process that previously stored the process data in the freed memory unit.

5. The method for allocating memory of claim 1, wherein denoting comprises:

marking the freed memory unit as read-only without unmapping the freed memory from virtual memory; and

clearing a dirty bit associated with the freed memory unit to indicate that the process data does not need to be preserved.

6. The method for allocating memory of claim 1, wherein denoting comprises:

updating a local free memory pool to indicate that the freed memory unit is available for reuse; and

wherein determining comprises;

determining whether the local free memory pool is suitable for use by the process associated by the request.

7. A system for allocating memory comprising:

a memory containing instructions; and

a processor, operably connected to the memory, that executes the instructions to perform operations comprising;

denoting a freed memory unit of a physical memory as available for reuse, without altering process data in the freed memory unit;

receiving a request, associated with a process, for a memory allocation from the physical memory;

determining, in response to the request, whether the process data contained in the freed memory unit is disclosable to the process associated with the request; and

allocating the freed memory unit to the process, if the determining indicates that the process data is disclosable to the process;

or

allocating a memory unit other than the freed memory unit to the process, if the determining indicates that the process data is not disclosable to the process.

8. The system for allocating memory of claim 7, wherein determining comprises:

determining that the process data is disclosable to the process when the process data was previously stored by the process in the freed memory unit.

9. The system for allocating memory of claim 7, wherein determining comprises:

determining that the process data is disclosable to the process when a user associated with the process is the user associated with a second process that previously stored the process data in the freed memory unit.

10. The system for allocating memory of claim 7, wherein determining comprises:

determining that the process data is disclosable to the process when a security context associated with the process is compatible with the security context associated with a second process that previously stored the process data in the freed memory unit.

11. The system for allocating memory of claim 7, wherein denoting comprises:

marking the freed memory unit as read-only without unmapping the freed memory from virtual memory; and

clearing a dirty bit associated with the freed memory unit to indicate that the process data does not need to be preserved.

12. The system for allocating memory of claim 7, wherein denoting comprises:

updating a local free memory pool to indicate that the freed memory unit is available for reuse; and

wherein determining comprises;

determining whether the local free memory pool is suitable for use by the process associated by the request.

13. A method, implemented by a processor, for allocating memory comprising:

placing a freed memory unit of a physical memory in a local reuse pool, without altering process data in the freed memory unit;

receiving a request, associated with a first process, for a memory allocation from the physical memory;

if the process data contained in the freed memory unit is disclosable to the first process associated with the request, then allocating, by the processor and to the process, the freed memory unit from the local reuse pool; and

if the process data contained in the freed memory unit is not disclosable to the first process, then allocating, by the processor and to the process, a cleared memory unit;

wherein the cleared memory unit contains no usable data from a second process that previously used the cleared memory unit.

14. The method for allocating memory of claim 13, wherein the process data is disclosable to the first process when the process data was previously stored by the first process in the freed memory unit.

15. The method for allocating memory of claim 13, wherein the process data is disclosable to the first process when a user associated with the first process is the user associated with the second process that previously used the freed memory unit.

16. The method for allocating memory of claim 13, wherein the process data is disclosable to the first process when a security context associated with the first process is compatible with the security context associated with the second process that previously used the freed memory unit.

17. The method for allocating memory of claim 13, wherein placing further comprises:

marking the freed memory unit as read-only without unmapping the freed memory from virtual memory; and

clearing a dirty bit associated with the freed memory unit to indicate that the process data does not need to be preserved.

18. The method for allocating memory of claim 13, further comprising:

receiving an indication that a memory unit is available for reuse;

clearing the data in the memory unit to create the cleared memory unit.