Shared cache for point-to-point connected processing nodes

• US 8,151,057 B1
• Filed: 07/15/2004
• Issued: 04/03/2012
• Est. Priority Date: 07/15/2004
• Status: Active Grant

• Current Assignee: Oracle America, Inc. (Oracle Corporation)
• Original Assignee: Oracle America, Inc. (Oracle Corporation)
• Inventors: Deva, Shailendra, Koster, Michael J., O'Krafka, Brian W.
• Primary Examiner(s): Bragdon, Reginald
• Assistant Examiner(s): Ruiz, Aracelis
• Application Number:
  US10/891,594
• Time in Patent Office: 2,819 Days
• Field of Search: 711/130, 711/146
• US Class Current: 711/130
• CPC Class Codes: G06F 12/0833 in combination with broadcast means (e.g. for invalidation or updating)

Abstract

A shared cache is point-to-point connected to a plurality of point-to-point connected processing nodes, wherein the processing nodes may be integrated circuits or multiprocessing systems. In response to a local cache miss, a requesting processing node issues a broadcast for requested data which is observed by the shared cache. If the shared cache has a copy of the requested data, the shared cache forwards the copy of the requested data to the requesting processing node.

Claims

1. A system comprising:

a first plurality of point-to-point connected processing nodes comprising;

a processing node configured to;

broadcast a cache-miss data request for a data item;

receive a first response to the cache-miss data request comprising the data item; and

discard, after receiving the first response, a second response to the cache-miss data request;

a second plurality of point-to-point connected processing nodes;

a passive backplane comprising;

a first shared memory point-to-point connecting the first plurality of processing nodes and the second plurality of processing nodes and configured to;

observe the cache-miss data request for the data item;

identify the data item within the first shared memory;

transmit the first response comprising the data item to the processing node; and

a second shared memory point-to-point connecting the first plurality of processing nodes and the second plurality of processing nodes, wherein the second shared memory is address-interleaved with the first shared memory; and

a third shared memory disposed within the second plurality of processing nodes and configured to;

snoop the first response; and

update a local version of the data item in the third shared memory based on the first response.

2. The system of claim 1, wherein the first plurality of processing nodes and the second plurality of processing nodes are associated with a grid topology.

3. The system of claim 1, wherein the second shared memory is associated with even cache lines and the first shared memory is associated with odd cache lines.

4. The system of claim 1, wherein the first plurality of processing nodes are interconnected using point-to-point interconnects having a bandwidth exceeding a 16-bit 1 MHz interconnect.

5. The system of claim 1, wherein each of the first plurality of processing nodes and the second plurality of processing nodes are symmetric multiprocessing (SMP) computer systems.

6. The system of claim 1, further comprising:

a fourth shared memory disposed within the second plurality of processing nodes.

7. The system of claim 1, wherein the first shared memory is at least 32 MB in size.

8. The system of claim 1, wherein the first response is associated with a cache-to-cache transfer.

9. The system of claim 1, wherein address-interleaving interconnects cache lines of the first shared memory and the second shared memory.

10. The system of claim 1, wherein the first plurality of processing nodes reside in a first near-commodity modular shelf server and the second plurality of processing nodes reside in a second near-commodity modular shelf server.

11. A computer-implemented method comprising:

detecting, by a processing node of a first plurality of point-to-point connected processing nodes, a cache miss;

broadcasting, by the processing node and in response to the cache-miss, a cache-miss data request, for a data item;

receiving, by a memory selected from a group consisting of a first shared memory and a second shared memory residing on a passive backplane, the data request for the data item, wherein the first shared memory is address-interleaved with the second shared memory, and wherein the first shared memory and the second shared memory are connected to the first plurality of processing nodes and a second plurality of processing nodes by a plurality of point-to-point connections of the passive backplane;

generating, by the memory, a first response comprising the data item to satisfy the data request;

receiving, by the processing node, the first response comprising the data item;

discarding, by the processing node, a second response to satisfy the data request after receiving the first response;

snooping the first response by a third shared memory disposed within the second plurality of processing nodes; and

updating, by the third shared memory, a local version of the data item based on the first response.

12. The method of claim 11, wherein the first plurality of processing nodes use a point-to-point interconnect having a bandwidth exceeding a 16-bit 1 MHz interconnect.

13. The method of claim 11, wherein the first plurality of processing nodes and the second plurality of processing nodes are associated with a grid topology.

14. The method of claim 11, wherein each of the first plurality of processing nodes and the second plurality of processing nodes are symmetric multiprocessing (SMP) computer systems.

15. The method of claim 11, wherein the second shared memory is associated with even cache lines and the first shared memory is associated with odd cache lines.

16. The method of claim 11, wherein the first response is associated with a cache-to-cache transfer.

17. The method of claim 11, wherein address-interleaving interconnects cache lines of the first shared memory and the second shared memory.

18. The method of claim 11, wherein the first plurality of processing nodes reside in a first near-commodity modular shelf server and the second plurality of processing nodes reside in a second near-commodity modular shelf server.