COOPERATIVE MECHANISM FOR EFFICIENT APPLICATION MEMORY ALLOCATION

• US 20090172337A1
• Filed: 03/06/2009
• Published: 07/02/2009
• 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
• Granted Patent: US 8,321,638 B2
• Time in Patent Office: Days
• US Class Current: 711/170
• 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 for allocating memory freed by applications in a computer system having an operating system (O/S), said method comprising:

a) designating a status of said one or more freed memory units previously associated with an application as available for reuse;

b) organizing one or more freed memory units having said available for reuse status into one or more free memory pools, wherein freed memory units in a pool are directly allocated to an application requiring backing physical memory store without the O/S deleting data in the freed memory units.

2. The method as claimed in claim 1, further comprising maintaining information about said application and said free memory pools, said information used to directly allocate said freed memory units to an application.

3. The method as claimed in claim 2, wherein said maintained information comprises information representing how one or more pools are organized, said one or more pools being organized according to a criteria selected from the following:

a process, a user, a security context, a processor, an applications node'"'"'s status as being a Non-Uniform Memory Access (NUMA) node, or, a memory zone where fixed size freed memory units are made available.

4. The method as claimed in claim 3, wherein a pool is her organized according to one or more dimensions based on a combination of said criteria.

5. The method as claimed in claim 2, wherein prior to said designating, performing:

implementing a system function to determine whether said freed memory spans one or more fixed size freed memory units in virtual memory space, said fixed size memory unit corresponding to a size of a physical memory page Frame.

6. The method as claimed in claim 1, further comprising:

receiving, by said O/S instruction to allocate memory for an application; and

, in response, said O/S determining if a pool having freed memory units available for reuse will not result in a data security breach if data included in said freed memory units of said pool is allocated to said application; and

, if no data security breach results, allocating said freed memory units of that pool to said application without the O/S expending overhead of deleting data included in said freed memory units.

7. The method as claimed in claim 6, wherein said determining if a pool having said freed memory units available for reuse will not result in a data security breach, is based on one or more of the following:

a process, a user, or a security context, or combinations thereof.

8. The method as claimed in claim 6, wherein said O/S tracks freed memory units that are available system-wide, wherein if it is determined that no pool having freed memory units available for that reuse will not result in a data security breach, said method including:

determining if there are any freed memory units available in system-wide free memory for allocation; and

, if no freed memory units are available system-wide, reclaiming said freed memory units from a pool.

9. The method as claimed in claim 8, wherein said freed memory units designated as available for reuse from a pool are reclaimed based on criteria including:

a size of said free memory pool;

an allocation rate from the pool;

a rate at which memory is freed into the pool;

a net allocation rate of the pool; and

a length of time memory has been assigned to the pool, or combinations of these.

10. The method as claimed in claim 8, further comprising:

determining whether freed memory units marked as available for reuse in a free memory pool are available for reclaiming and, if it is determined that freed memory units marked as available for reuse from a free memory pool are not available for reclaiming, said O/S further;

designating the freed memory units as no longer being available for reuse; and

, removing the freed memory unit from the free memory pool.

11. The method as claimed in claim 10, further including:

invoking pageout mechanism for transferring contents of said freed memory units removed from said pool into another storage media thereby increasing availability of system-wide memory.

12. A method for managing memory freed by processes executing in a virtual memory space in a computer system implementing means for mapping virtual memory addresses into physical memory locations accessible by an operating system (O/S), said method comprising:

receiving, by said O/S, an indication of freed memory in said virtual memory space that spans one or more fixed size memory units in physical memory; and

,

adding said fixed size memory units to a free memory pool, said fixed size memory units in a free memory pool being directly allocatable to a process requiring backing physical memory store without the O/S deleting data in the freed fixed size memory units.

13. The method as claimed in claim 12, further comprising:

maintaining information about said process and one or more free memory pools having fixed size memory units, said information used to directly allocate said freed fixed size memory units to a process.

14. The method as claimed in claim 13, wherein said one or more free memory pools having freed fixed size memory units are organized according to criteria selected from the following:

a process, a user, a security context, a processor, an applications node'"'"'s status as being a Non-Uniform Memory Access (NUMA) node, and, a memory zone where fixed size freed memory units are made available, or combinations thereof.

15. The method as claimed in claim 13, wherein said fixed size memory unit comprises a physical memory page frame, and prior to said O/S adding one or more fixed size memory units into a free memory pool, rendering said physical memory page frame as available for reuse by a process while leaving said physical memory page frame mapped to said process'"'"'s virtual memory space.

16. The method as claimed in claim 15, wherein said O/S receives a page fault exception, and in response, said O/S:

determining whether a free memory pool includes a physical memory page available for reuse, and if said free memory pool includes a physical memory page frame available for reuse;

removing said page from said free memory pool;

determining whether the freed memory page is to be used by a process that freed it, and allocating said page if said page is to be used by said freeing process.

17. The method as claimed in claim 16, wherein if it is determined that a memory page frame is not available for reuse in said free memory pool:

determining if a memory page frame is available in a system wide free memory pool, and if a page frame is available in a system wide free memory pool,

deleting data included in said memory page frame; and

,

allocating memory page frames from a system wide free memory pool for said process.

18. The method as claimed in claim 17, wherein if a memory page frame is not available in a system wide free memory pool, invoking pageout mechanism for increasing availability of system-wide free memory pages.

19. The method as claimed in claim 12, wherein said O/S tracks fixed size memory units that are available system-wide, said method including:

determining whether an amount of fixed size memory units tracked system-wide is below a threshold amount.

20. The method as claimed in claim 19, wherein if said amount of fixed size memory units tracked system-wide is below a threshold amount said O/S:

determining if a suitable free page pool to reclaim freed fixed size memory units from; and

,

reclaiming said freed fixed size memory units from that free memory pool.

21. The method as claimed in claim 20, wherein said freed memory units designated as available for reuse from a pool are reclaimed based on criteria including:

a size of said free memory pool;

an allocation rate from the pool;

a rate at which memory is freed into the pool;

a net allocation rate of the pool; and

a length of time memory has been assigned to the pool, or combinations of these.

22. The method as claimed in claim 20, wherein if it is determined that no page frames are available in said free memory pools, or no suitable free page pool exists to reclaim freed memory pages from, then invoking pageout mechanism for increasing availability of system-wide free memory pages.

23. The method as claimed in claim 19, wherein a process having freed fixed size memory units marked available for reuse is associated with an executing parent process, wherein upon determination of said process terminating, said method further comprising the step of:

determining that said process does not present a security conflict with said parent process; and

,

upon determining no security conflict exists, releasing said freed fixed size memory units marked available for reuse to said parent process.

24. The method as claimed in claim 23, further comprising:

the step of releasing said freed fixed size memory units into said system wide free memory pool when a process terminates, wherein said freed fixed size memory units of said system-wide free pool are available system-wide.

25. The method as claimed in claim 24, wherein said process having freed fixed size memory units marked available for reuse is associated with an executing parent process, wherein when said process terminates, said method further comprising:

comparing computer system performance for executing a step of releasing said freed fixed size memory units marked available for reuse by a terminating process to its parent process against a computer system performance for executing a step of releasing said freed fixed size memory units marked available for reuse into a global free pool of fixed size memory units when said process terminates; and

,

choosing a method of releasing said freed fixed size memory units marked available for reuse according to said performance comparison.

26. The method as claimed in claim 25, wherein said comparing comprises:

measuring the computer system performance for releasing said freed fixed size memory units marked available for reuse at one of;

a computer system start-up time, or at a computer system run time when said freed fixed size memory units marked available for reuse are to be allocated.