Cues : File Subsystem Data Streams

We present a system call which enables directing high performance data transfers with in-kernel streams. The streams are de ned and run using abstract data types called Cues, formed over the Unix le subsystem. The system call, named cue() , returns a descriptor, which can be used to write requests to the newly created stream. These requests de ne the ow of the stream. The abstraction simpli es the design of applications that transfer large amounts of data from les or devices. It also enables high throughput when multiple transfers are in progress. Cue code is compact, modular, and portable. This model also results in a simple mechanism for remotely cueing data ow using standard connections with peer processes. The implementation and tests are also described in this paper. Also with Department of Computer Science. Also with Institute of Advanced Computer Studies. Also with Department of Electrical Engineering. This material is based upon work supported in part by the National Science Foundation under Grant No. NSF EEC 94-02384, and by the Center for Satellite and Hybrid Communication Networks under NASA contract NAGW-2777, by the University of Maryland Institute of Advanced Computing Studies, by ARPA under Grant No. F30602{93{C{0177, Maryland Industrial Partnerships and Loral Corporation. Part of the design for this work was also done by the rst author as a summer intern at AT&T Bell Laboratories, Murray Hill in Summer '94.