Reduced Size Register View Data Structure for Microprocessor Context Switching

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Solution Overview

Problem

Current processor architectures face inefficiencies in handling multiple threads due to the need for context switching and the overhead of duplicating architecture state elements for each thread, which increases complexity, power consumption, and area requirements, while also struggling with fine-grain parallelism and efficient threading in non-threaded software codes.

Innovation Solution

Implementing a reduced size register view data structure in a microprocessor by grouping instructions into blocks, using register templates to track dependencies, and storing only snapshots or deltas of register template changes to manage the machine state efficiently, thereby reducing the need for extensive context switching and improving parallel execution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If hardware duplicates all architecture state elements for each supported thread, then context switch is eliminated, but area, power and complexity increase

Engineering Contradiction:

Improvecontext switch timeVSAvoidhardware complexity

Core Design Contradiction:

Loss of timeVSDevice complexity

Solution Approach 1:

The architecture state is segmented into multiple contexts (thread contexts, interrupt contexts, exception contexts) that can be independently managed. The register view is divided into snapshots corresponding to different instruction blocks, allowing selective restoration of only necessary state portions rather than duplicating entire register files for each thread.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of physically duplicating entire register files for each thread, the patent creates virtual copies through snapshot data structures. Each snapshot captures the register state at a particular point, and these snapshots are stored in a compact format that can be rapidly restored without requiring full hardware duplication.

Inventive Principle:

Principle #26Copying

2Loss of time

If hardware duplicates all architecture state elements for each supported thread, then context switch is eliminated, but area requirements increase

Engineering Contradiction:

Improvecontext switch timeVSAvoidregister file area

Core Design Contradiction:

Loss of timeVSArea of stationary object

Solution Approach 1:

The register state is segmented into snapshots that can be selectively stored and restored. Only the necessary snapshot data is retained in the register view, rather than maintaining complete duplicate register files for each possible thread context, significantly reducing the required storage area.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the parameter representation from full register values to compact snapshot identifiers and delta information. This parameter transformation allows the same functional capability (thread context management) to be achieved with much smaller storage requirements.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If context switching is performed frequently for fine grain parallelism, then parallel execution is enabled, but overhead increases

Engineering Contradiction:

Improveparallel execution efficiencyVSAvoidcontext switch overhead

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

The system performs preliminary actions by pre-capturing register snapshots at instruction block boundaries and pre-organizing them in the register view data structure. When a context switch is needed, the restored state is already prepared and readily available, eliminating the need for time-consuming save/restore operations during actual thread switching.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent creates lightweight virtual copies of register states through snapshot data structures rather than physical register file duplications. These snapshot copies can be rapidly switched between threads, enabling fine-grain parallelism with minimal overhead compared to traditional context switching mechanisms.

Inventive Principle:

Principle #26Copying

4Productivity

If the number of software threads exceeds hardware-supported threads, then more parallelism is achieved, but context switching becomes necessary

Engineering Contradiction:

Improvethread parallelismVSAvoidcontext switch frequency

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

The register view data structure serves multiple functions: it acts as both a thread context storage mechanism and a snapshot management system for out-of-order execution. This universal structure can handle any number of software threads by dynamically allocating snapshot entries, allowing the same hardware to support more threads than traditionally possible without dedicated context switch hardware.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS10503514B2Method for implementing a reduced size register view data structure in a microprocessor

Publication Date: 2019.12.10 INTEL CORP

AI summary

A method of managing a reduced size register view data structure in a processor, where the method includes receiving an incoming instruction sequence using a global front end, grouping instructions from the incoming instruction sequence to form instruction blocks, populating a register view data structure, wherein the register view data structure stores register information references by the instruction blocks as a set of register templates, generating a set of snapshots of the register templates to reduce a size of the register view data structure, and tracking a state of the processor to handle a branch miss-prediction using the register view data structure in accordance with execution of the instruction blocks.