Instruction for pre-fetching data and releasing cache lines

• US 8,683,138 B2
• Filed: 01/06/2012
• Issued: 03/25/2014
• Est. Priority Date: 12/12/2007
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Greiner, Dan F, Slegel, Timothy J
• Primary Examiner(s): BATAILLE, PIERRE MICHE
• Application Number:
  US13/344,636
• Publication Number:
  US 20120144125A1
• Time in Patent Office: 809 Days
• Field of Search: 711/130, 711/137, 711/E12.004, 711/125, 711/E12.057, 712/E9.055, 712/207
• US Class Current: 711/137
• CPC Class Codes: G06F 12/0862 with prefetch
• CPC Class Codes: G06F 2212/6028 Prefetching based on hints or prefetch instructions
• CPC Class Codes: G06F 9/30047 Prefetch instructions; cache control instructions
• CPC Class Codes: G06F 9/383 Operand prefetching cache prefetching G06F12/0862
• CPC Class Codes: G06F 9/3832 Value prediction for operands; operand history buffers

Abstract

A prefetch data machine instruction having an M field performs a function on a cache line of data specifying an address of an operand. The operation comprises either prefetching a cache line of data from memory to a cache or reducing the access ownership of store and fetch or fetch only of the cache line in the cache or a combination thereof. The address of the operand is either based on a register value or the program counter value pointing to the prefetch data machine instruction.

Claims

1. A computer system for executing a prefetch data machine instruction, defined for a computer architecture, the prefetch data machine instruction specifying a cache action to be performed, the system comprising:

a memory;

a cache in communication with the memory; and

a processor in communication with the cache and the memory, the processor comprising an instruction fetching unit for accessing instructions from memory and one or more execution units for executing accessed instructions, the processor configured to perform a method comprising;

executing, by the processor, the prefetch data machine instruction, the prefetch data machine instruction comprising an option field, the execution comprising;

determining, by the processor, whether the option field specifies a data prefetch cache action or a cache line ownership operation, the data prefetch cache action for prefetching a cache line of data from memory to the cache, the cache line ownership operation for changing cache access ownership of a line of data in the cache;

using a value of an immediate field of the prefetch data machine instruction to determine an address of an operand in memory; and

based on determining the option field specifies a data prefetch cache action, the execution comprising performing, by the processor, the data prefetch cache action comprising fetching to the cache, a line of data associated with the address of the operand in memory; and

based on determining the option field specifies a cache line ownership operation, the execution not-fetching the line of data to the cache or otherwise modifying content of the line of data in the cache, the execution only performing, by the processor, a cache line ownership operation, on a cache line already in the cache.

2. The computer system according to claim 1, wherein the performing further comprises:

based on the option field the cache line ownership operation, performing a determined cache ownership action on the cache line in the cache, the cache ownership action comprising;

based on the determined cache ownership action being a release store access ownership action, changing access ownership of the cache line to a fetch access ownership, the store access ownership indicating that the processor intends to store to the cache line, the fetch access ownership indicating that the processor intends to fetch data from the cache line; and

based on the determined cache ownership action being a release fetch access ownership action, releasing access ownership, the released access ownership indicating that the processor does not intend to access to the cache line.

3. The computer system according to claim 2, wherein the store access ownership indicates the cache line is not available to other processors, and wherein the fetch access ownership indicates the cache line may be shared by other processors.

4. The computer system according to claim 2, wherein the cache ownership action further comprises:

based on the determined cache ownership action being a modified access ownership action, changing access ownership of the cache line to indicate the cache line has been modified; and

based on the determined cache ownership action being an owned access ownership action, changing access ownership of the cache line to indicate the cache line is owned.

5. The computer system according to claim 1, wherein the prefetch data machine instruction further comprises operand information, the execution further comprising:

interpreting the option field to determine whether to perform the data prefetch cache action or the cache line ownership operation; and

wherein the function performed further comprises, based on the option field determined cache action being a data prefetch action, prefetching said operand from memory at said determined addressed into said cache line of said cache.

6. The computer system according to claim 5, wherein the function performed further comprises:

based on the option field being a first value, performing no cache action;

based on the option field being a second value, prefetching, to the cache, data specified by the operand address for fetch access ownership wherein the cache line access ownership is set as fetch access ownership; and

based on the option field being a third value, prefetching, to the cache, data, specified by the operand address for store access ownership wherein the cache line access ownership is set as store access ownership.

7. The computer system according to claim 5, wherein the function performed comprises:

based on the option field being a fourth value and store access ownership being available, prefetching to the cache, data specified by the operand address for store access ownership wherein the cache line access ownership is set as store access ownership; and

based on the option field being the fourth value and store access ownership being not-available, prefetching to the cache, data specified by the operand address for store access ownership wherein the cache line access ownership is set as fetch access ownership.

8. The computer system according to claim 1, further comprising:

interpreting the prefetch data machine instruction to identify a predetermined software routine for emulating the operation of the prefetch data machine instruction on an underlying central processing unit having a different instruction set architecture, the predetermined software routine comprising a plurality of instructions; and

executing the predetermined software routine to execute the prefetch data machine instruction.

18. The computer program product according to claim 1, wherein the performing further comprises:

based on the option field the cache line ownership operation, performing a determined cache ownership action on the cache line in the cache, the cache ownership action comprising;

based on the determined cache ownership action being a release store access ownership action, changing access ownership of the cache line to a fetch access ownership, the store access ownership indicating that the processor intends to store to the cache line, the fetch access ownership indicating that the processor intends to fetch data from the cache line; and

based on the determined cache ownership action being a release fetch access ownership action, releasing access ownership, the released access ownership indicating that the processor does not intend to access to the cache line.

19. The computer program product according to claim 18, wherein the store access ownership indicates the cache line is not available to other processors, and wherein the fetch access ownership indicates the cache line may be shared by other processors.

20. The computer program product according to claim 18, wherein the cache ownership action further comprises:

based on the determined cache ownership action being a modified access ownership action, changing access ownership of the cache line to indicate the cache line has been modified; and

based on the determined cache ownership action being, an owned access ownership action, changing access ownership of the cache line to indicate the cache line is owned.

9. A computer implemented method for executing a prefetch data machine instruction, defined for a computer architecture, the prefetch data machine instruction specifying a cache action to be performed, the method comprising:

executing, by the processor, the prefetch data machine instruction, the prefetch data machine instruction comprising an option field, the execution comprising;

determining, by the processor, whether the option field specifies a data prefetch cache action or a cache line ownership operation, the data prefetch cache action for prefetching a cache line of data from memory to the cache, the cache line ownership operation for changing cache access ownership of a line of data in the cache;

using a value of an immediate field of the prefetch data machine instruction to determine an address of an operand in memory; and

based on determining the option field specifies a data prefetch cache action, the execution comprising performing, by the processor, the data prefetch cache action comprising fetching to the cache, a line of data associated with the address of the operand in memory; and

based on determining the option field specifies a cache line ownership operation, the execution not-fetching the line of data to the cache or otherwise modifying content of the line of data in the cache, the execution only performing, by the processor, a cache line ownership operation, on a cache line already in the cache.

10. The method according to claim 9, wherein the performing further comprises:

based on the option field the cache line ownership operation, performing a determined cache ownership action on the cache line in the cache, the cache ownership action comprising;

based on the determined cache ownership action being a release store access ownership action, changing access ownership of the cache line to a fetch access ownership, the store access ownership indicating that the processor intends to store to the cache line, the fetch access ownership indicating that the processor intends to fetch data from the cache line; and

based on the determined cache ownership action being a release fetch access ownership action, releasing access ownership, the released access ownership indicating that the processor does not intend to access to the cache line.

11. The method according to claim 10, wherein the store access ownership indicates the cache line is not available to other processors, and wherein the fetch access ownership indicates the cache line may be shared by other processors.

12. The method according to claim 10, wherein the cache ownership action further comprises:

based on the determined cache ownership action being a modified access ownership action, changing access ownership of the cache line to indicate the cache line has been modified; and

based on the determined cache ownership action being an owned access ownership action, changing access ownership of the cache line to indicate the cache line is owned.

13. The method according to claim 9, wherein the prefetch data machine instruction further comprises operand information, the execution further comprising:

interpreting the option field to determine whether to perform the data prefetch cache action or the cache line ownership operation; and

wherein the function performed further comprises, based on the option field determined cache action being a data prefetch action, prefetching said operand from memory at said determined addressed into said cache line of said cache.

14. The method according to claim 13, wherein the function performed further comprises:

based on the option field being a first value, performing no cache action;

based on the option field being a second value, prefetching, to the cache, data specified by the operand address for fetch access ownership wherein the cache line access ownership is set as fetch access ownership; and

based on the option field being a third value, prefetching, to the cache, data, specified by the operand address for store access ownership wherein the cache line access ownership is set as store access ownership.

15. The method according to claim 13, wherein the function performed comprises:

based on the option field being a fourth value and store access ownership being available, prefetching to the cache, data specified by the operand address for store access ownership wherein the cache line access ownership is set as store access ownership; and

based on the option field being the fourth value and store access ownership being not-available, prefetching to the cache, data specified by the operand address for store access ownership wherein the cache line access ownership is set as fetch access ownership.

16. The computer program product according to claim 9, further comprising:

interpreting the prefetch data machine instruction to identify a predetermined software routine for emulating the operation of the prefetch data machine instruction on an underlying central processing unit having a different instruction set architecture, the predetermined software routine comprising a plurality of instructions; and

executing the predetermined software routine to execute the prefetch data machine instruction.

17. A computer program product for executing a prefetch data machine instruction, defined for a computer architecture, the prefetch data machine instruction specifying a cache action to be performed, the computer program product comprising:

a storage medium readable by a processing circuit and storing instructions for execution by the processing circuit of a processor for performing a method comprising;

executing, by the processor, the prefetch data machine instruction, the prefetch data machine instruction comprising an option field and an immediate field, the execution comprising;

determining, by the processor, whether the option field specifies a data prefetch cache action or a cache line ownership operation, the data prefetch cache action for prefetching a cache line of data from memory to the cache, the cache line ownership operation for changing cache access ownership of a line of data in the cache;

using a value of the immediate field of the prefetch data machine instruction to determine an address of an operand in memory; and

based on determining the option field specifies a data prefetch cache action, the execution comprising performing, by the processor, the data prefetch cache action comprising fetching to the cache, a line of data associated with the address of the operand in memory; and

based on determining the option field specifies a cache line ownership operation, the execution not-fetching the line of data to the cache or otherwise modifying content of the line of data in the cache, the execution only performing, by the processor, a cache line ownership operation, on a cache line already in the cache.

21. The computer program product according to claim 17, wherein the prefetch data machine instruction further comprises operand information, the execution further comprising:

interpreting the option field to determine whether to perform the data prefetch cache action or the cache line ownership operation; and

wherein the function performed further comprises, based on the option field determined cache action being a data prefetch action, prefetching said operand from memory at said determined addressed into said cache line of said cache.

22. The computer program product according to claim 21, wherein the function performed further comprises:

based on the option field being a first value, performing no cache action;

based on the option field being a second value, prefetching, to the cache, data specified by the operand address for fetch access ownership wherein the cache line access ownership is set as fetch access ownership; and

based on the option field being a third value, prefetching, to the cache, data, specified by the operand address for store access ownership wherein the cache line access ownership is set as store access ownership.

23. The computer program product according to claim 21, wherein the function performed comprises:

based on the option field being a fourth value and store access ownership being available, prefetching to the cache, data specified by the operand address for store access ownership wherein the cache line access ownership is set as store access ownership; and

based on the option field being the fourth value and store access ownership being not-available, prefetching to the cache, data specified by the operand address for store access ownership wherein the cache line access ownership is set as fetch access ownership.

24. The computer program product according to claim 17, further comprising:

interpreting the prefetch data machine instruction to identify a predetermined software routine for emulating the operation of the prefetch data machine instruction on an underlying central processing unit having a different instruction set architecture, the predetermined software routine comprising a plurality of instructions; and

executing the predetermined software routine to execute the prefetch data machine instruction.