Berkeley Unix Going Through Changes


June 1987

Significant changes to Berkeley Unix are underway, say computer scientists at the University of California's Berkeley campus, but it will probably be a couple of years before users see those changes fully implemented. Marshall McKusick, a scientist with UCB's Computer Systems Research Group, told Microbytes that three major areas of Unix 4.3 BSD are undergoing development: the virtual memory system, the file system interface, and the protocol layering interface.

According to McKusick, "the file system is pretty much operational now," and, because the work is being completed "serially," modifications will be released incrementally. This file system interface uses the 4.3 BSD name-lookup calling convention, but otherwise resembles Sun Microsystems' Virtual File System (VPS) interface.

Future versions of Berkeley Unix, said McKusick, who is working with Michael Karels on the project, will "support virtual memory space at least as great as the sum of sizes of physical memory plus swap space." Additionally, processes will probably be allowed to map files and device memory into their address spaces and to share memory with other processes.

The protocol layering interface McKusick and Karels are working on will be based on the simple stackable-line discipline of the Eighth Edition Unix rather than the Streams implementation of System V, release 3. McKusick and Karels plan to implement a socket interface rather than a character device interface, and protocols in the kernel will handle the demultiplexing.

McKusick added that "a major change we have made is that we are basing our releases on hardware made by Computer Consoles Inc. We did that because DEC [4.3 BSD is based on Digital Equipment Corp. hardware] was getting to the point where they felt they were competing with us. It was getting difficult to get documentation and so on. Our next beta release will likely be based on CCI." McKusick said that "we are making it [Unix] more portable by doing this. ... By going to completely different hardware, we've had to face a number of issues that manufacturers have had to face all along."

Copyright 1987