SYSTEMS AND METHODS FOR PROVIDING DYNAMIC MEMORY PRE-FETCH

• US 20080183903A1
• Filed: 01/29/2007
• Published: 07/31/2008
• Est. Priority Date: 01/29/2007
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Gower, Kevin C., VanStee, Dustin J.
• Granted Patent: US 7,603,526 B2
• Time in Patent Office: Days
• US Class Current: 710/5
• CPC Class Codes: G06F 13/161 with latency improvement

Abstract

Systems and methods for providing dynamic memory pre-fetch. Embodiments include a hub device including an input command stream interface and an adaptive pre-fetch logical unit (APLU). The input command stream interface detects commands from a memory controller directed to one or more memory devices that are connected to the hub device. The APLU independently analyzes the commands to determine access patterns to the memory devices. The APLU also dynamically selects between enabling a pre-fetch function and disabling the pre-fetch function for the memory devices based on the results of the analysis.

Claims

1. A hub device comprising:

an input command stream interface for detecting commands from a memory controller directed to one or more memory devices that are connected to the hub device; and

an adaptive pre-fetch logical unit (APLU) for independently analyzing the commands to determine access patterns to the memory devices and for dynamically selecting between enabling a pre-fetch function and disabling the pre-fetch function for the memory devices based on results of the analysis.

2. The hub device of claim 1 wherein the access patterns are read access patterns.

3. The hub device of claim 1 wherein the analyzing includes predicting expected addresses of future commands from the memory controller based on the access patterns wherein the pre-fetch function is enabled when the accuracy of the predicting is equal to or above an enable pre-fetch threshold and the pre-fetch function is disabled when the accuracy of the predicting is equal to or below a disable pre-fetch threshold.

4. The hub device of claim 1 wherein the pre-fetch function dispatches pre-fetch read commands having a lower priority than the read commands from the memory controller.

5. The hub device of claim 1 further comprising a pre-fetch buffer utilized by the pre-fetch function for storing pre-fetched data and addresses.

6. The hub device of claim 5 wherein data coherency is maintained in the pre-fetch buffer during write operations.

7. The hub device of claim 1 wherein the analyzing and selecting applies to one bank on one of the memory devices.

8. The hub device of claim 1 wherein the analyzing and selecting applied to one of the memory devices is independent of the analyzing and selecting applied to an other of the memory devices.

9. The hub device of claim 1 wherein the analyzing and selecting applied to one bank in one of the memory devices is independent of the analyzing and selecting applied to an other bank in the memory device.

10. The hub device of claim 1 wherein the analyzing and selecting applies to all of the memory devices.

11. The hub device of claim 1 wherein the commands include pending commands located in a memory command buffer.

12. The hub device of claim 11 wherein the APLU further reorders the pending commands in the memory command buffer to alter future access patterns.

13. A method for selecting a pre-fetch mode, the method comprising:

detecting commands from a memory controller directed to one or more memory devices attached to a hub device;

analyzing the commands to determine access patterns to the memory devices; and

dynamically selecting between enabling a pre-fetch function and disabling the pre-fetch function for the memory devices based on results of the analysis.

14. The method of claim 13 wherein the access patterns are read access patterns.

15. The method of claim 13 wherein the analyzing includes predicting expected addresses of future commands from the memory controller based on the access patterns, wherein the pre-fetch function is enabled when the accuracy of the predicting is equal to or above an enable pre-fetch threshold and the pre-fetch function is disabled when the accuracy of the predicting is equal to or below a disable pre-fetch threshold.

16. The method of claim 15 wherein the predicting is performed using an algorithm for detecting and predicting strided addresses.

17. The method of claim 13 wherein the pre-fetch function dispatches pre-fetch read commands having a lower priority than the read commands from the memory controller.

18. The method of claim 13 wherein the pre-fetch function stores pre-fetched data and addresses in a pre-fetch buffer.

19. The method of claim 18 wherein data coherency is maintained in the pre-fetch buffer during write operations.

20. The method of claim 13 wherein the analyzing and selecting applies to one bank on one of the memory devices.

21. The method of claim 13 wherein the analyzing and selecting applied to one of the memory devices is independent of the analyzing and selecting applied to an other of the memory devices.

22. The method of claim 13 wherein the analyzing and selecting applied to one bank in one of the memory devices is independent of the analyzing and selecting applied to an other bank in the memory device.

23. The method of claim 13 wherein the analyzing and selecting applies to all of the memory devices.

24. The method of claim 13 wherein the commands include pending commands located in a memory command buffer.

25. The method of claim 24 wherein the pending commands are reordered to alter future access patterns.

26. A memory system comprising:

a memory controller;

one or more memory devices; and

a memory hub device in communication with the memory controller and the memory devices, the memory hub device comprising;

an input command stream interface for detecting commands from the memory controller directed to the memory devices; and

an APLU for independently analyzing the commands to determine access patterns to the memory devices and for dynamically selecting between enabling a pre-fetch function and disabling the pre-fetch function for the memory devices based on results of the analysis.

27. A memory subsystem comprising:

one or more memory devices; and

a memory hub device comprising;

an input command stream interface for detecting commands from a memory controller directed to the memory devices; and

an APLU for independently analyzing the commands to determine access patterns to the memory devices and for dynamically selecting between enabling a pre-fetch function and disabling the pre-fetch function for the memory devices based on results of the analysis.