The Alloc Stream Facility : A Redesign of Application - Level Stream

This paper describes the design and implementation of a new application level I/O facility, called the Alloc Stream Facility. The Alloc Stream Facility has several key advantages. First, performance is substantially improved as a result of a) the structure of the facility that allows it to take advantage of system speciic features like mapped les, and b) a reduction in data copying and the number of I/O system calls. Second , the facility is designed for multi-threaded applications running on multiprocessors and allows for a high degree of concurrency. Finally, the facility can support a variety of I/O interfaces, including stdio, emulated Unix I/O, ASI, and C++ streams, in a way that allows applications to freely intermix calls to the diierent interfaces, resulting in improved code reusability. We show that on several Unix workstation platforms the performance of Unix applications using the Alloc Stream Facility can be substantially better that when the applications use the original I/O facilities.