Bridges performing remote reads and writes as uncacheable coherent

• US 20050080948A1
• Filed: 10/14/2003
• Published: 04/14/2005
• Est. Priority Date: 11/20/2001
• Status: Active Grant

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Rowlands, Joseph B.
• Granted Patent: US 7,752,281 B2
• Time in Patent Office: Days
• US Class Current: 710/36
• CPC Class Codes: G06F 12/0813 with a network or matrix configuration
• CPC Class Codes: G06F 12/0815 Cache consistency protocols
• CPC Class Codes: G06F 13/4027 using bus bridges G06F13/4022 takes precedence
• CPC Class Codes: G06F 2212/621 Coherency control relating to peripheral accessing, e.g. from DMA or I/O device

Abstract

A system and method for improving the bandwidth for data read and write operations in a multi-node system by using uncacheable read and write commands to a home node in the multi-node system so that the home node can determine whether the commands needs to enter the coherent memory space. In one embodiment where nodes are connected via HT interfaces, posted commands are used to transmit uncacheable write commands over the HT fabric to a remote home node so that no response is required from the home node. When both cacheable and uncacheable memory operations are mixed in a multi-node system, a producer-consumer software model may be used to require that the data and flag must be co-located in the home node'"'"'s memory and that the producer write both the data and flag using regular HT I/O commands. In one embodiment, a system for managing data in multiple data processing devices using common data paths comprises a first data processing system comprising a memory, wherein the memory comprises a cacheable coherent memory space; and a second data processing system communicatively coupled to the first data processing system with the second data processing system comprising at least one bridge, wherein the bridge is operable to perform an uncacheable remote access to the cacheable coherent memory space of the first data processing system. In some embodiments, the access performed by the bridge comprises a data write to the memory of the first data processing system for incorporation into the cacheable coherent memory space of the first data system. In other embodiments, the access performed by the bridge comprises a data read from the cacheable coherent memory space of the first data system.

Claims

1. A system for managing data in multiple data processing devices using common data paths, comprising:

a first data processing system comprising a memory, wherein said memory comprises a cacheable coherent memory space; and

a second data processing system communicatively coupled to said first data processing system, said second data processing system comprising at least one bridge, wherein said bridge is operable to perform an uncacheable remote access to said cacheable coherent memory space of said first data processing system.

2. The system of claim 1, wherein the access performed by said bridge comprises a data write to said memory of said first data processing system for incorporation into said cacheable coherent memory space of said first data system.

3. The system of claim 1, wherein the access performed by said bridge comprises a data read from said cacheable coherent memory space of said first data system.

4. The system of claim 2, wherein the data written by said bridge during said uncacheable remote access participates in a cacheable coherent memory protocol in said cacheable memory space.

5. The system of claim 4, wherein said converted data in said cacheable coherent memory space is accessed by an agent subsequent to said conversion.

6. The system of claim 5, wherein said remote access by said bridge and said subsequent access by said agent conform to a producer-consumer protocol, wherein said bridge corresponds to the producer and said agent corresponds to the consumer of said producer-consumer protocol.

7. The system of claim 6, wherein said data written by said bridge comprises a payload memory and a flag memory, with said flag and said payload memory both residing in a node defined by said first data system.

8. The system of claim 7, wherein the remote access by said bridge to perform said data write is performed in accordance with a set of predetermined ordering rules.

9. The system of claim 8, wherein said predetermined ordering rules for performing said remote access data write comprise:

non-posted requests cannot bypass posted requests;

responses cannot bypass posted requests; and

posted requests cannot bypass posted requests.

10. A method for managing data in multiple data processing devices using common data paths, comprising:

establishing a coherent memory space in a first data processing system; and

accessing said coherent memory space with a second data processing system communicatively coupled to said first data processing system, said second data processing system comprising at least one bridge, wherein said bridge performs an uncacheable remote access to said cacheable coherent memory space of said first data processing system.

11. The method of claim 10, wherein the access performed by said bridge comprises a data write to said memory of said first data processing system for incorporation into said cacheable coherent memory space of said first data system.

12. The method of claim 10, wherein the access performed by said bridge comprises a data read from said cacheable coherent memory space of said first data system.

13. The method of claim 11, wherein the data written by said bridge during said uncacheable remote access participates in a cacheable coherent memory protocol in said cacheable memory space.

14. The method of claim 13, wherein said converted data in said cacheable coherent memory space is accessed by an agent subsequent to said conversion.

15. The method of claim 14, wherein said remote access by said bridge and said subsequent access by said agent conform to a producer-consumer protocol, wherein said bridge corresponds to the producer and said agent corresponds to the consumer of said producer-consumer protocol.

16. The method of claim 15, wherein said data written by said bridge comprises a payload memory and a flag memory, with said flag and said payload memory both residing in a node defined by said first data system.

17. The method of claim 16, wherein the remote access by said bridge to perform said data write is performed in accordance with a set of predetermined ordering rules.

18. The method of claim 17, wherein said predetermined ordering rules for performing said remote access data write comprise:

non-posted requests cannot bypass posted requests;

responses cannot bypass posted requests; and

posted requests cannot bypass posted requests.