Processor Mode Transition Prediction Reducing Latency

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Solution Overview

Problem

Processor operational mode transitions, such as between 64-bit and 32-bit modes, result in performance penalties due to the need to serialize instruction execution and complete older operations before transitioning, especially when mode changes are frequent.

Innovation Solution

Implementing mode transition prediction to allow early transition into the target mode by anticipating operational mode changes, including for interrupts, exceptions, and other control flow transfers, thereby reducing latency and improving performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the processor serializes instruction execution to complete older operations before transitioning modes, then mode transition correctness is ensured, but processor performance deteriorates due to execution stalls

Engineering Contradiction:

Improvemode transition correctnessVSAvoidprocessor performance

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent applies preliminary action by predicting the target operational mode before the mode transition actually occurs. The prediction logic determines the target mode in advance of the control flow transfer, allowing the processor to prepare for the transition proactively rather than reactively, thereby reducing the need for serialization and improving performance

Inventive Principle:

Principle #10Preliminary action

2Reliability

If the processor completes older operations before transitioning modes, then instruction execution correctness is maintained, but execution time increases due to serialization requirements

Engineering Contradiction:

Improveinstruction execution correctnessVSAvoidexecution time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The prediction logic determines the target operational mode in advance of the control flow transfer, allowing the processor to begin preparing for the mode transition before the current operations complete. This preliminary determination reduces the time penalty associated with mode transitions by eliminating or reducing serialization requirements

Inventive Principle:

Principle #10Preliminary action

3Adaptability or versatility

If frequent mode transitions are performed, then program functionality is achieved, but performance penalty increases due to repeated serialization

Engineering Contradiction:

Improveprogram functionalityVSAvoidperformance

Core Design Contradiction:

Adaptability or versatilityVSProductivity

Solution Approach 1:

By predicting the target operational mode in advance of each control flow transfer, the processor can prepare for mode transitions proactively. This is particularly beneficial for frequent mode transitions, as the prediction logic can quickly determine the target mode and minimize the performance impact of repeated transitions

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The prediction logic uses feedback from control flow transfer information to determine the target operational mode. This feedback mechanism allows the processor to adapt to frequent mode transitions by using the control flow information to predict and prepare for the next mode, reducing the cumulative performance penalty

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS11354128B2Optimized mode transitions through predicting target state

Publication Date: 2022.06.07 INTEL CORP

AI summary

In one embodiment, software executing on a data processing system that is capable of performing dynamic operational mode transitions can realize performance improvements by predicting transitions between modes and/or predicting aspects of a new operational mode. Such prediction can allow the processor to begin an early transition into the target mode. The mode transition prediction principles can be applied for various processor mode transitions including 64-bit to 32-bit mode transitions, interrupts, exceptions, traps, virtualization mode transfers, system management mode transfers, and/or secure execution mode transfers.