Shared file system cache in a virtual machine or LPAR environment

• US 20050223005A1
• Filed: 06/07/2005
• Published: 10/06/2005
• Est. Priority Date: 04/29/2003
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Tkatschow, Xenia, Shultz, Steven
• Granted Patent: US 7,831,977 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 12/084 with a shared cache
• CPC Class Codes: G06F 2009/45566 Nested virtual machines
• CPC Class Codes: G06F 2009/45583 Memory management, e.g. access or allocation
• CPC Class Codes: G06F 9/45558 Hypervisor-specific management and integration aspects
• CPC Class Codes: G06F 9/526 Mutual exclusion algorithms

Abstract

Computer system, method and program for defining first and second virtual machines and a memory shared by the first and second virtual machines. A filesystem cache resides in the shared memory. A lock structure resides in the shared memory to record which virtual machine, if any, currently has an exclusive lock for writing to the cache. The first virtual machine includes a first program function to acquire the exclusive lock when available by manipulation of the lock structure, and a second program function active after the first virtual machine acquires the exclusive lock, to write to the cache. The lock structure is directly accessible by the first program function. The cache is directly accessible by the second program function. The second virtual machine includes a third program function to acquire the exclusive lock when available by manipulation of the lock structure, and a fourth program function active after the second virtual machine acquires the exclusive lock, to write to the cache. The lock structure is directly accessible by the third program function. The cache is directly accessible by the fourth program function. Another computer system, method and program is embodied in logical partitions of a real computer, instead of virtual machines.

Claims

1. A computer system defining first and second virtual machines and a memory shared by said first and second virtual machines, said computer system comprising:

a filesystem cache in said shared memory;

a lock structure in said shared memory to record which virtual machine, if any, currently has an exclusive lock for writing to said cache;

said first virtual machine includes a first program function to acquire said exclusive lock when available by manipulation of said lock structure, and a second program function active after said first virtual machine acquires said exclusive lock, to write to said cache, said lock structure being directly accessible by said first program function, said cache being directly accessible by said second program function; and

said second virtual machine includes a third program function to acquire said exclusive lock when available by manipulation of said lock structure, and a fourth program function active after said second virtual machine acquires said exclusive lock, to write to said cache, said lock structure being directly accessible by said third program function, said cache being directly accessible by said fourth program function.

2. A system as set forth in claim 1 further comprising said storage.

3. A system as set forth in claim 1 wherein said shared filesystem cache stores both file data and associated directory data.

4. A system as set forth in claim 1 wherein said first and second program functions reside in a memory private to said first virtual machine such that said second virtual machine cannot invoke said first or second program functions, and said third and fourth program functions reside in a memory private to said second virtual machine such that said first virtual machine cannot invoke said third or fourth program functions.

5. A computer system as set forth in claim 1 wherein said first program function is initiated to acquire said lock by a request from a first application within said first virtual machine to write to a file in said storage, and said third program function is initiated to acquire said lock by a request from a second application within said second virtual machine to write to said file.

6. A computer system as set forth in claim 1 wherein said lock structure also records which virtual machine, if any, is currently waiting for said exclusive lock for writing to said cache.

7. A system as set forth in claim 1 wherein:

said lock structure also records which virtual machine, if any, currently has a nonexclusive lock for reading from said cache;

said first program function can acquire said nonexclusive lock when available by manipulation of said lock structure, and said second program function is active after said first virtual machine acquires said nonexclusive lock to read from said cache; and

said third program function can acquire said nonexclusive lock when available by manipulation of said lock structure, and said fourth program function is active after said second virtual machine acquires said nonexclusive lock to read from said cache.

8. A computer system as set forth in claim 7 wherein both said first and second virtual machines can concurrently hold said nonexclusive lock.

9. A computer system as set forth in claim 7 wherein said lock structure also records which virtual machine, if any, is currently waiting for said nonexclusive lock for reading from said cache.

10. A computer system as set forth in claim 1 further comprising:

a fifth program function, active after said first virtual machine acquires said exclusive lock, to outpage from said cache to storage when needed to make room for a page requested to be written by said first virtual machine and to inpage said requested page from said storage when not resident in said cache, said cache being directly accessible by said fifth program function; and

a sixth program function, active after said second virtual machine acquires said exclusive lock, to outpage from said cache to storage when needed to make room for a page requested to be written by said second virtual machine and to inpage said requested page from said storage when not resident in said cache, said cache being directly accessible by said sixth program function.

11. A computer program product for execution within a computer system defining first and second virtual machines and a memory shared by said first and second virtual machines, said computer program product comprising:

a computer readable medium;

first program instructions to define a filesystem cache in said shared memory;

second program instructions to define a lock structure in said shared memory to record which virtual machine, if any, currently has an exclusive lock for writing to said cache;

third program instructions for execution in said first virtual machine to acquire said exclusive lock when available by manipulation of said lock structure, and fourth program instructions for execution in said first virtual machine active after said first virtual machine acquires said exclusive lock, to write to said cache, said lock structure being directly accessible by said third program function, said cache being directly accessible by said fourth program function; and

fifth program instructions for execution in said second virtual machine to acquire said exclusive lock when available by manipulation of said lock structure, and sixth program instructions for execution in said second virtual machine active after said second virtual machine acquires said exclusive lock, to write to said cache, said lock structure being directly accessible by said fifth program instructions, said cache being directly accessible by said sixth program instructions; and

wherein

said first, second, third, fourth, fifth and sixth program instructions are stored on said medium.

12. A computer program product as set forth in claim 11 further comprising:

seventh program instructions for execution in said first virtual machine active after said first virtual machine acquires said exclusive lock, to outpage from said cache to storage when needed to make room for a page requested to be written by said first virtual machine and to inpage said requested page from said storage when not resident in said cache, said cache being directly accessible by said fifth program function; and

eighth program instructions for execution in said second virtual machine, active after said second virtual machine acquires said exclusive lock, to outpage from said cache to storage when needed to make room for a page requested to be written by said second virtual machine and to inpage said requested page from said storage when not resident in said cache, said cache being directly accessible by said sixth program function; and

wherein

said seventh and eighth program instructions are stored on said medium.

13. A computer system defining first and second logical partitions and a memory shared by said first and second logical partitions, said computer system comprising:

a filesystem cache in said shared memory;

a lock structure in said shared memory to record which logical partition, if any, currently has an exclusive lock for writing to said cache;

said first logical partition includes a first program function to acquire said exclusive lock when available by manipulation of said lock structure, and a second program function active after said first logical partition acquires said exclusive lock, to write to said cache, said lock structure being directly accessible by said first program function, said cache being directly accessible by said second program function; and

said second logical partition includes a third program function to acquire said exclusive lock when available by manipulation of said lock structure, and a fourth program function active after said second logical partition acquires said exclusive lock, to write to said cache, said lock structure being directly accessible by said third program function, said cache being directly accessible by said fourth program function.

14. A system as set forth in claim 13 wherein said shared filesystem cache stores both file data and associated directory data.

15. A system as set forth in claim 13 wherein said first and second program functions reside in a memory private to said first logical partition such that said second logical partition cannot invoke said first or second program functions, and said third and fourth program functions reside in a memory private to said second logical partition such that said first logical partition cannot invoke said third or fourth program functions.

16. A computer system as set forth in claim 13 wherein said first program function is initiated to acquire said lock by a request from a first application within said first logical partition to write to a file in said storage, and said third program function is initiated to acquire said lock by a request from a second application within said second logical partition to write to said file.

17. A system as set forth in claim 13 wherein:

said lock structure also records which logical partition, if any, currently has a nonexclusive lock for reading from said cache;

said first program function can acquire said nonexclusive lock when available by manipulation of said lock structure, and said second program function is active after said first logical partition acquires said nonexclusive lock to read from said cache; and

said third program function can acquire said nonexclusive lock when available by manipulation of said lock structure, and said fourth program function is active after said second logical partition acquires said nonexclusive lock to read from said cache.

18. A computer system as set forth in claim 13 further comprising:

a fifth program function, active after said first logical partition acquires said exclusive lock, to outpage from said cache to storage when needed to make room for a page requested to be written by said first logical partition and to inpage said requested page from said storage when not resident in said cache, said cache being directly accessible by said fifth program function; and

a sixth program function, active after said second logical partition acquires said exclusive lock, to outpage from said cache to storage when needed to make room for a page requested to be written by said second logical partition and to inpage said requested page from said storage when not resident in said cache, said cache being directly accessible by said sixth program function.

19. A computer program product for execution within a computer system defining first and second logical partitions and a memory shared by said first and second logical partitions, said computer program product comprising:

a computer readable medium;

first program instructions to define a filesystem cache in said shared memory;

second program instructions to define a lock structure in said shared memory to record which logical partition, if any, currently has an exclusive lock for writing to said cache;

third program instructions for execution in said first logical partition to acquire said exclusive lock when available by manipulation of said lock structure, and fourth program instructions for execution in said first logical partition active after said first logical partition acquires said exclusive lock, to write to said cache, said lock structure being directly accessible by said third program function, said cache being directly accessible by said fourth program function; and

fifth program instructions for execution in said second logical partition to acquire said exclusive lock when available by manipulation of said lock structure, and sixth program instructions for execution in said second logical partition active after said second logical partition acquires said exclusive lock, to write to said cache, said lock structure being directly accessible by said fifth program instructions, said cache being directly accessible by said sixth program instructions; and

wherein

said first, second, third, fourth, fifth and sixth program instructions are stored on said medium.

20. A computer program product as set forth in claim 19 further comprising:

seventh program instructions for execution in said first logical partition active after said first logical partition acquires said exclusive lock, to outpage from said cache to storage when needed to make room for a page requested to be written by said first logical partition and to inpage said requested page from said storage when not resident in said cache, said cache being directly accessible by said fifth program function; and

eighth program instructions for execution in said second logical partition, active after said second logical partition acquires said exclusive lock, to outpage from said cache to storage when needed to make room for a page requested to be written by said second logical partition and to inpage said requested page from said storage when not resident in said cache, said cache being directly accessible by said sixth program function; and

wherein

said seventh and eighth program instructions are stored on said medium.