Thread De-emphasis for Multithreaded Processor Stall Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In multithreaded processors, stalls in the instruction pipeline due to cache misses or memory transactions can lead to reduced efficiency, as a stall in one thread can delay the execution of other threads, and existing methods for monitoring and addressing these stalls are resource-intensive and inefficient.
Innovation Solution
A method is introduced where a thread de-emphasis instruction is executed to lower the priority of a thread with pending memory transactions above a threshold, allowing other threads with higher priority to access processor resources, thereby reducing the likelihood of pipeline stalls. This is achieved through a thread control module that adjusts priority based on the number of pending transactions and restores priority once they are resolved.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the processor executes threads based on equal priority scheduling, then all threads can be processed fairly, but pipeline stalls occur when one thread has pending memory transactions, reducing overall processor efficiency
Solution Approach 1:
The patent implements dynamic thread priority adjustment based on the number of pending memory transactions. The thread control module continuously monitors pending transactions and adjusts thread priority levels dynamically, allowing threads with fewer pending transactions to execute ahead and prevent pipeline stalls, while maintaining fairness when threads have similar transaction counts.
Solution Approach 2:
The system employs feedback mechanisms where the thread control module monitors the instruction pipeline for stalls and pending memory transactions, then adjusts thread priority accordingly. This closed-loop control ensures that priority allocation responds to actual pipeline conditions, preventing stalls by promoting threads that are ready to execute while demoting those causing delays.
2Productivity
If the processor monitors instruction pipeline for stalls and adjusts thread priority dynamically, then pipeline efficiency improves, but additional overhead is introduced at the processor
Solution Approach 1:
The thread control module performs multiple functions: it schedules threads based on priority, monitors pending memory transactions, detects pipeline stalls, and adjusts priority levels. By consolidating these functions into a single control module, the patent reduces overall processor overhead while maintaining dynamic priority adjustment capabilities that improve pipeline efficiency.
Solution Approach 2:
The system uses existing processor resources and thread metadata (pending transaction counts) that are already maintained for other purposes. The thread control module leverages this existing information infrastructure to make priority decisions without requiring extensive additional monitoring hardware or complex data collection mechanisms.
3Speed
If threads with pending memory transactions are given high priority, then their execution is expedited, but other threads experience delays reducing overall throughput
Solution Approach 1:
The patent changes the priority parameter of threads based on their pending memory transaction count. Threads with fewer pending transactions are assigned higher priority to execute quickly and free up pipeline resources, while threads with many pending transactions receive lower priority. This parameter adjustment optimizes both individual thread speed and overall processor throughput by balancing execution across multiple threads.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A technique for scheduling execution of threads [221, 222] at a processor [102] is disclosed. The technique includes executing a thread de-emphasis instruction [220] of a thread [221] that de-emphasizes the thread until the number of pending memory transactions [330], such as cache misses, associated with the thread are at or below a threshold [320]. While the thread is de-emphasized, other threads at the processor that have a higher priority can be executed or assigned system resources. Accordingly, the likelihood of a stall in the processor is reduced.