ABSTRACT

Carnegie Mellon University Parallel Data Lab Technical Report CMU-PDL-03-107, December, 2003.

Design and Implementation of a Freeblock Subsystem

Eno Thereska, Jiri Schindler, Christopher R. Lumb, John Bucy, Brandon Salmon, Gregory R. Ganger

Electrical and Computer Engineering
Carnegie Mellon University
Pittsburgh, PA 15213

http://www.pdl.cmu.edu/

Freeblock scheduling allows background applications to access the disk without affecting primary system activities. This paper describes a complete freeblock subsystem, implemented in FreeBSD. It details new space- and time-efficient algorithms that make freeblock scheduling useful in practice. It also describes algorithm extensions for using idle time, dealing with multi-zone disks, reducing fragmentation, and avoiding starvation of the inner- and outer-most tracks. The result is an infrastructure that efficiently provides steady disk access rates to background applications, across a range of foreground usage patterns.

KEYWORDS: scheduling, disks, asynchronous, interfaces

FULL PAPER: pdf / postscript