I/O Hub Atomic Operation Descriptor Control
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Solution Overview
Problem
Existing systems face challenges in performing atomic I/O operations across multiprocessor systems without requiring specific atomic operations in the processor architecture, leading to inefficiencies and interconnect exclusivity penalties.
Innovation Solution
An I/O hub with control logic that issues atomic operations on the I/O device interconnect, using descriptors to specify target devices and operations, allowing for atomic operations without relying on processor-supported atomic instructions, and enabling completion control by the I/O device interconnect rather than the system interconnect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If atomic operations are implemented using system interconnect exclusivity, then data integrity is maintained, but interconnect under-utilization penalties increase
Solution Approach 1:
The patent segments the atomic operation control into two independent parts: the system interconnect handles only the trigger event and descriptor transfer (non-blocking), while the I/O device hub manages the actual atomic operation execution and completion signaling. This segmentation allows the system interconnect to remain non-exclusive and highly utilized, while the I/O device hub ensures data integrity through atomic operations on the device bus.
2Productivity
If processor architecture includes native atomic operations, then atomic I/O operations can be performed directly, but compatibility with devices requiring specific atomic operations is limited
Solution Approach 1:
The I/O device hub acts as an intermediary between the processor and the I/O device. It receives atomic operation descriptors from the processor, translates them into appropriate atomic operations for the specific device, and manages the atomic operation execution. This intermediary approach allows the processor to use generic atomic operation interfaces while the hub adapts to different device-specific atomic operation requirements, enhancing both performance and compatibility.
3Reliability
If system interconnect exclusivity is used for atomic operations, then operation completion is controlled by the interconnect, but processing delays increase
Solution Approach 1:
The patent extracts the atomic operation completion control function from the system interconnect and relocates it to the I/O device hub. The system interconnect only handles the initial trigger event and descriptor transfer, then releases control to the hub. The hub manages the atomic operation execution and completion signaling independently, eliminating the need for system interconnect exclusivity and reducing processing delays while maintaining reliable completion control.
Data Source
AI summary
Atomic operations within an I/O device are supported by processor architectures that are not required to include specific atomic instructions, by issuing the atomic operations from an I/O hub. A descriptor that specifies the atomic operation and a target address is retrieved by, or sent to, the hub. A trigger event, which may be a programmed I/O write to the hub with an address of the descriptor, or the contents of the descriptor itself, causes the I/O hub to issue the atomic operation. When the atomic operation is complete on the I/O device interconnect, the result is returned to the hub and a host is notified. The host then retrieves the results of the atomic operation from the hub. The host notification can be performed by interrupt or by polling the hub until a status change is detected.