Doorbell Exception Masking for Virtual Processor Scheduling
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Solution Overview
Problem
The inefficiency in data processing systems utilizing virtual processors is exacerbated by multiple exceptions related to the same virtual processor, which can reduce overall system efficiency and require access to restricted resources for disabling and enabling doorbell exceptions.
Innovation Solution
A data processing apparatus and method that includes exception control circuitry to issue doorbell exceptions only for active virtual processors, with a mechanism to mask virtual processors, thereby disregarding doorbell exceptions for masked processors, reducing unnecessary scheduling operations and resource access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If doorbell exceptions are raised for multiple exceptions relating to the same virtual processor, then the virtual processor can be scheduled for activation, but overall system efficiency is reduced due to repeated scheduling operations
Solution Approach 1:
The patent extracts the problematic repeated scheduling operations by introducing a masking mechanism that filters out doorbell exceptions for virtual processors that are already scheduled or active. This removes the harmful repetition while preserving necessary exception handling for unscheduled processors.
Solution Approach 2:
The patent implements a feedback mechanism through the masking system that tracks the scheduling state of virtual processors. When a virtual processor is scheduled or activated, it is masked to prevent further doorbell exceptions from triggering redundant scheduling operations, creating a self-regulating system.
2Adaptability or versatility
If the procedure for disabling and enabling doorbell exceptions is implemented, then restricted resources can be controlled, but access to restricted resources is required which reduces overall efficiency
Solution Approach 1:
The masking mechanism operates autonomously without requiring access to restricted resources for disabling or enabling doorbell exceptions. The system self-manages the filtering of exceptions based on the masking state, eliminating the need for resource-restricted control procedures.
3Productivity
If virtual processors are suspended and activated frequently, then task isolation and processor utilization are improved, but repeated scheduling operations increase resource usage
Solution Approach 1:
The patent converts the potentially harmful effect of repeated doorbell exceptions into a benefit by using the masking mechanism to identify and eliminate redundant scheduling operations. The same exception routing infrastructure that enables flexible processor activation is used to prevent wasteful repeated scheduling.
Data Source
AI summary
There is provided a data processing apparatus that includes processing circuitry for executing instructions relating to an active virtual processor in a plurality of virtual processors. Exception control circuitry receives an external exception associated with a target virtual processor in the plurality of virtual processors and when the target virtual processor is other than the active virtual processor, it issues a doorbell exception to cause a scheduling operation to schedule the target virtual processor to be the active virtual processor. Storage circuitry stores an indication of a set of masked virtual processors and the scheduling operation is adapted to disregard doorbell exceptions in respect of the set of masked virtual processors.