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Towards Effective User-Controlled Scheduling for Microkernel-Based Systems

Towards Effective User-Controlled Scheduling for Microkernel-Based Systems

Jan Stoess


ACM SIGOPS Operating System Review, Special Topics on Secure Small-Kernel Systems, July 2007

Date: 07-2007


With µ-kernel based systems becoming more and more prevalent, the demand for extensible resource management raises - and with it the demand for flexible thread scheduling. In this paper, we investigate the benefits and costs of a µ-kernel that exports scheduling from the kernel to user level. A key idea of our approach is to involve the user level whenever the µ-kernel encounters a situation that is ambiguous with respect to scheduling, and to permit the kernel to resolve the ambiguity based on user decisions. A further key aspect is that we rely on a generic, protection domain neutral interface between kernel and applications.

For evaluation, we have developed a hierarchical user level scheduling architecture for the L4 µ-kernel, and a virtualization environment running on its top. Our environment supports Linux 2.6.9 guest operating systems on IA-32 processors. Experiments indicate an application overhead between 0 and 10 percent compared to a pure in-kernel scheduler solution, but also demonstrate that our architecture enables effective and accurate user-directed scheduling.


  author = {Jan Stoess},
  type = {publication},
  title = {Towards Effective User-Controlled Scheduling for Microkernel-Based Systems},
  publisher = {ACM},
  journal = {Operating Systems Review},
  volume = {41},
  number = {3},
  month = jul,
  year = 2007,
  affiliation = {University of Karlsruhe, Germany}