Hardware Accelerator Direct Communication Interface
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Solution Overview
Problem
Current hardware accelerators lack a scalable mechanism for device-to-device communication, leading to complexities in software design and the need for custom drivers, as they primarily interface with processors rather than supporting direct communication between devices, which hinders efficient operation chaining and data passing.
Innovation Solution
Implementing a hardware-based solution that enables direct communication between accelerators and I/O devices without processor intervention, using a common interface for device-to-device communication, allowing any device to submit work to another without prior knowledge of its specifics, and separating control transport from data transport to simplify software and hardware design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If hardware accelerators interface primarily with processors, then processor control and management is simplified, but device-to-device communication capability and system throughput are limited
Solution Approach 1:
The communication interface is segmented into separate control transport and data transport channels. Control transport handles command and status communication between processors and accelerators, while data transport enables direct device-to-device data movement. This segmentation allows processors to maintain simplified control while accelerators achieve high-speed direct communication for improved system throughput.
Solution Approach 2:
A communication interface acts as an intermediary between processors and hardware accelerators, enabling both processor-controlled operations and direct device-to-device communication. This intermediary layer manages the dual-mode operation, allowing accelerators to communicate with processors when needed while also enabling direct accelerator-to-accelerator and accelerator-to-I/O device communication paths that bypass the processor for improved throughput.
2Productivity
If hardware accelerators support direct device-to-device communication, then system throughput and performance are enhanced, but software design complexity and driver requirements increase
Solution Approach 1:
The communication interface provides universal functionality by supporting multiple communication modes through a single unified interface: processor-to-accelerator control, accelerator-to-accelerator data transfer, and accelerator-to-I/O device communication. This multi-functional design enables diverse communication patterns without requiring separate specialized interfaces for each mode, thereby reducing software design complexity while maintaining high throughput capabilities.
Solution Approach 2:
The communication interface incorporates feedback mechanisms that provide status information and completion notifications to processors and software drivers. This feedback enables drivers to implement efficient polling or interrupt-driven models without requiring complex custom logic, as the interface automatically manages data transfer states and notifies software when operations complete, reducing driver complexity while enabling high-performance direct communication.
3Reliability
If custom drivers are implemented for each accelerator configuration, then device-specific functionality is optimized, but software maintenance burden and development time increase
Solution Approach 1:
A universal driver model is implemented that works across different accelerator configurations through the standardized communication interface. The interface abstracts device-specific details while providing consistent control and data transport mechanisms, allowing a single driver framework to support multiple accelerator types and configurations. This universality maintains reliable device functionality while dramatically reducing software development and maintenance burdens compared to custom drivers for each configuration.
Solution Approach 2:
The communication interface uses descriptor-based data structures that can be copied and reused across different communication operations and device configurations. Buffer descriptors, command descriptors, and status structures are standardized templates that can be instantiated for different accelerators without requiring custom driver code, enabling reliable device-specific functionality through configuration rather than custom software development.
4Reliability
If processor intervention is required for all accelerator communication, then system control is centralized, but context switch rates and cache misses increase
Solution Approach 1:
Communication operations are segmented into control plane operations that require processor intervention and data plane operations that occur directly between devices. The communication interface segregates control transport (processor-managed) from data transport (direct device-to-device), allowing time-critical data transfers to occur without processor involvement. This segmentation maintains centralized system control for configuration and monitoring while eliminating unnecessary context switches and cache misses during actual data communication.
Solution Approach 2:
The communication interface enables accelerators to service their own communication needs directly without processor intervention. Accelerators can autonomously exchange data through the interface, manage their own buffer descriptors, and handle data transport independently. This self-service capability reduces processor workload, minimizes context switches, and decreases cache misses while maintaining system control through the interface's standardized protocols and the processor's ability to configure and monitor operations.
Data Source
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AI summary
Methods and apparatuses relating to offload operations are described. In one embodiment, a hardware processor includes a core to execute a thread and offload an operation; and a first and second hardware accelerator to execute the operation, wherein the first and second hardware accelerator are coupled to shared buffers to store output data from the first hardware accelerator and provide the output data as input data to the second hardware accelerator, an input buffer descriptor array of the second hardware accelerator with an entry for each respective shared buffer, an input buffer response descriptor array of the second hardware accelerator with a corresponding response entry for each respective shared buffer, an output buffer descriptor array of the first hardware accelerator with an entry for each respective shared buffer, and an output buffer response descriptor array of the first hardware accelerator with a corresponding response entry for each respective shared buffer.