UMS Thread Context Migration via Directed Switches

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Solution Overview

Problem

The division of user mode schedulable (UMS) threads into user and kernel portions can cause difficulties during thread execution, leading to mismatches in identities and requiring special steps for smooth transitions between modes, which affects performance and resource usage.

Innovation Solution

Implementing directed switches that allow the user portion of a primary thread to switch to the user portion of a UMS thread, enabling execution in user mode, and then transferring to kernel mode with context information migration to ensure proper execution of the kernel portion, thereby optimizing thread execution and reducing processing overhead.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If UMS threads are divided into user and kernel portions, then user mode scheduling and concurrency are improved, but execution difficulties and identity mismatches occur during thread execution

Engineering Contradiction:

Improveuser mode scheduling efficiencyVSAvoidthread execution reliability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent introduces a directed switch mechanism as an intermediary between the user portion and kernel portion of UMS threads. This mediator ensures proper context migration and identity maintenance during mode transitions, resolving the reliability issues caused by direct division into user and kernel portions while preserving scheduling efficiency

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If context information is migrated during mode transitions, then proper thread execution is ensured, but processing overhead increases

Engineering Contradiction:

Improvethread execution correctnessVSAvoidprocessing overhead

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent implements preliminary context preparation where the user portion pre-establishes necessary context information before mode transition. This advance preparation reduces the amount of context migration required during actual mode switching, thereby ensuring execution correctness while minimizing processing overhead

Inventive Principle:

Principle #10Preliminary action

3Reliability

If special steps are taken for smooth transitions between modes, then execution difficulties are resolved, but performance is affected

Engineering Contradiction:

Improvemode transition stabilityVSAvoidthread execution performance

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent extracts and separates the transition management logic from the main thread execution path. By isolating the directed switch mechanism and context migration steps into distinct handling routines, the patent enables smooth mode transitions without interfering with the performance-critical execution paths, thus resolving the trade-off between transition stability and execution performance

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS8321874B2Intelligent context migration for user mode scheduling

Publication Date: 2012.11.27 MICROSOFT TECHNOLOGY LICENSING LLC

AI summary

Performing directed switches between user mode schedulable (UMS) threads and primary threads enable proper execution of the UMS threads. A primary thread user portion is switched to a UMS thread user portion so that the UMS thread user portion is executed in user mode via the primary thread user portion. The primary thread is then transferred into kernel mode via an implicit switch. A kernel portion of the UMS thread is then executed in kernel mode using the context information of a primary thread kernel portion.