Assigning and scheduling threads for multiple prioritized queues

Abstract

An operating system provides a pool of worker threads servicing multiple queues of requests at different priority levels. A concurrency controller limits the number of currently executing threads. The system tracks the number of currently executing threads above each priority level, and preempts operations of lower priority worker threads in favor of higher priority worker threads. A system can have multiple pools of worker threads, with each pool having its own priority queues and concurrency controller. A thread also can change its priority mid-operation. If a thread becomes lower priority and is currently active, then steps are taken to ensure priority inversion does not occur. In particular, the current thread for the now lower priority item can be preempted by a thread for a higher priority item and the preempted item is placed in the lower priority queue.

Description

Background technique [0001] In modern computing systems, it is common to have an operating system that allows a computer program to execute as multiple threads that share access to computing resources managed by the operating system. The operating system itself may also have multiple threads, referred to herein as worker threads, available to service requests from applications to operating system resources. [0002] There are several ways to manage the complexity of multiple applications competing for resources. Typically, queues are provided to manage requests from applications to use worker threads, such as requests to access resources using threads. If all requests are treated equally, the worker thread is assigned the first-coming request first. In some instances, some requests have higher priority than other requests. In such a case, a separate request queue is used for each priority level, and each priority level has its own pool of worker threads. The scheduler assi...

AI Technical Summary

Problems solved by technology

[0003] With such a system, each worker thread has a fixed priority and cannot change priority during execution; otherwise there is a risk of priority inversion

Also, with worker thread pools for each priority level, the number of priority levels is limited by system resources

Finally, such systems may experience dependency deadlocks

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