ULE scheduler explained

ULE scheduler
Author:	Jeff Roberson^[1]
Released:	^[2]
Programming Language:	C
Operating System:	FreeBSD
License:	BSD 2-clause

ULE is the default scheduler for the FreeBSD operating system (versions 7.1 and forward) for the i386 and AMD64 architectures.^[3] It was introduced in FreeBSD version 5,^[4] but it was disabled by default for a time in favor of the traditional BSD scheduler until it reached maturity. The original BSD scheduler does not make full use of SMP or SMT, which is important in modern computing environments. The primary goal of the ULE project is to make better use of SMP and SMT environments. ULE should improve performance in both uniprocessor and multiprocessor environments,^[5] as well as interactive response under heavy load.^[6] The user may switch between the BSD scheduler and ULE using a kernel compile-time tunable.^[7]

References

Sources

• Book: McKusick, M. K.. Neville-Neil. G. V.. The Design and Implementation of the FreeBSD Operating System. Pearson Education. 2004. 978-0-321-68003-7. 153.

Notes and References

1. Web site: sched_ule(4) man page. 2008-09-02.
2. Web site: FreeBSD CVS log . 27 August 2008 .
3. Web site: FreeBSD 7.1-RELEASE Release Announcement. retrieved on 5 January 2009
4. Web site: ULE: A Modern Scheduler for FreeBSD . 23 June 2008 .
5. Web site: FreeBSD 7.0-RELEASE Release Notes . 23 June 2008 .
6. Web site: ULE 2.0 . 2008-09-02 . Jeff . Roberson . dead . https://web.archive.org/web/20080517020426/http://jeffr-tech.livejournal.com/3729.html . 17 May 2008 .
7. Web site: FreeBSD Handbook. 2009-03-18. Chapter 8 Configuring the FreeBSD Kernel.