Real-Time Linux Kernel Scheduler

The -rt patchset, or just -rt, adds real-time scheduling capabilities to the Linux kernel.

The most important goal of a real-time kernel scheduler is to ensure SWSRPS. The scheduler in the CONFIG_PREEMPT_RT kernel uses push and pull algorithms to balance and correctly distribute real-time tasks across the system. Both the push and pull operations try to ensure that a real-time task gets an opportunity to run as soon as possible. Also, in order to reduce the performance and scalability impact that might result from increased contention of global variables, the scheduler uses the concept of root domains and CPU priority management. The scope of the global variables is reduced to a subset of CPUs as opposed to the entire system, resulting in significant reduction of cache penalties and performance improvement.

Legal Statement

This work represents the views of the author and does not necessarily represent the view of IBM. Linux is a copyright of Linus Torvalds. Other company, product and service names may be trademarks or service marks of others.

Ankita Garg, a computer science graduate from the P.E.S. Institute of Technology, works as a developer at the Linux Technology Centre, IBM India. She currently is working on the Real-Time Linux Kernel Project. You are welcome to send your comments and suggestions to


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