Program Order Queue for Multi-Queue Processor Dependency Management
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Processor architectures face challenges in managing instruction dependencies efficiently, leading to power inefficiencies in out-of-order processors and limited execution throughput in in-order processors, particularly due to the need for complex register renaming and dependency analysis logic.
Innovation Solution
The implementation of a program order queue (POQ) data structure that tracks the program order of instructions across multiple queues, allowing for eager instruction dispatch while preserving dependency integrity without the need for register renaming or power-hungry comparison logic, thereby enabling efficient handling of write-after-write, read-after-write, and read-after-read dependencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If out-of-order processor architecture is used to improve execution throughput, then instruction level parallelism increases, but power consumption increases significantly
Solution Approach 1:
The processor architecture segments instruction queues into multiple independent queues (e.g., queue 0, queue 1, etc.), each capable of independent operation. This segmentation allows the system to achieve out-of-order execution benefits while maintaining simpler, more power-efficient control logic within each queue, avoiding the need for complex global dependency management.
Solution Approach 2:
A program order queue (POQ) is introduced as an intermediary data structure to track instruction dependencies and program order information. The POQ acts as a mediator between multiple independent instruction queues and the execution units, enabling dependency management without requiring complex register renaming or comparison logic in each queue, thus reducing overall power consumption.
2Use of energy by moving object
If in-order processor architecture is used to maintain power efficiency, then power consumption is reduced, but execution throughput decreases
Solution Approach 1:
The processor implements dynamic instruction queue selection where the dispatcher can choose from multiple instruction queues based on readiness conditions and dependency status. This dynamic approach allows the system to maintain in-order execution within each queue (preserving power efficiency) while achieving out-of-order execution across queues (improving throughput), adapting to runtime conditions without complex global coordination.
3Adaptability or versatility
If register renaming logic is implemented to manage instruction dependencies, then dependency handling capability improves, but device complexity increases
Solution Approach 1:
Instead of implementing complex register renaming logic that creates and manages multiple renamed register versions, the system uses a program order queue that copies and tracks program order information and dependency relationships. This copying approach maintains dependency handling capability while avoiding the complexity of full register renaming infrastructure, including rename tables and allocation logic.
4Measurement precision
If content addressable memory-based schedulers are used to manage instruction dispatch, then instruction scheduling accuracy improves, but power consumption increases
Solution Approach 1:
The system replaces expensive content addressable memory (CAM) structures with simpler, disposable data structures in the program order queue that track instruction state and dependencies. These simpler structures are updated and discarded as instructions progress through execution, providing sufficient scheduling accuracy without the high power consumption associated with CAM-based schedulers that require continuous maintenance of large lookup tables.
Data Source
Figure 1A
Figure 1B
Figure 2A~2B
AI summary
In one embodiment, an apparatus includes: a plurality of registers; a first instruction queue to store first instructions; a second instruction queue to store second instructions; a program order queue having a plurality of portions each associated with one of the plurality of registers, each of the portions having entries to store a state of an instruction, the state comprising an encoding of a use of the register by the instruction and a source instruction queue for the instruction; and a dispatcher to dispatch for execution the first and second instructions from the first and second instruction queues based at least in part on information stored in the program order queue, to manage instruction dependencies between the first instructions and the second instructions. Other embodiments are described and claimed.