Pre-execution Unit for Command Stream Latency Reduction
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Solution Overview
Problem
Data processing systems face inefficiencies in command stream execution due to memory access latency and changes in control flow, which hinder throughput as the prefetching mechanism is unaware of control flow changes until executed, leading to latency 'bubbles' and reduced execution speed.
Innovation Solution
A data processing system with a pre-execution unit that interprets and acts on commands before they reach the command stream execution unit, allowing for early execution of certain commands and prefetching of data, thereby reducing latency and improving throughput by anticipating control flow changes and memory operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If commands are read from command stream storage into the accelerator before execution, then the accelerator can execute commands, but memory access latency reduces command stream execution throughput
Solution Approach 1:
The patent applies preliminary action by implementing a prefetching mechanism that reads commands from command stream storage into the accelerator before they are actually needed for execution. The command stream execution unit identifies upcoming commands and triggers prefetch operations to load these commands into the accelerator's memory in advance, thereby reducing the impact of memory access latency on overall execution throughput.
2Productivity
If the prefetching mechanism operates without knowledge of control flow changes, then it can continuously prefetch commands, but it creates latency bubbles when control flow changes occur
Solution Approach 1:
The patent implements feedback by having the command stream execution unit monitor control flow changes in real-time and provide this information back to the prefetching mechanism. When the execution unit detects a control flow change (such as a branch or jump instruction), it signals the prefetching mechanism to adjust its prefetching behavior accordingly, preventing the creation of latency bubbles caused by prefetching incorrect or unnecessary commands.
3Productivity
If commands are executed sequentially in the command stream execution unit, then execution is simple to manage, but execution speed is reduced due to memory access latency
Solution Approach 1:
The patent applies preliminary action by prefetching multiple commands into the accelerator's memory before the command stream execution unit needs to execute them. This overlapping of command fetch and execution operations allows the execution unit to continuously process commands without stalling for memory access, thereby improving execution speed while maintaining sequential execution simplicity.
Data Source
AI summary
A data processing system in which a host processor prepares command streams for causing an accelerator of the data processing system to perform processing tasks for an application executing on the host processor, each command stream including a sequence of commands for implementation by a command stream execution unit of the accelerator. A pre-execution unit is provided that is operable to interpret commands fetched from command stream storage before the command is provided to the command stream execution unit for implementation to determine whether the pre-execution unit is able to perform an action in response to the command and, when the pre-execution unit is able to do so, to perform an action in response to the command.