info-ridge@ucbvax.UUCP (12/12/85)
Recently there has been some discussion in this news group about the capabilities of ROS with respect to a multi-user environment. I believe some history and an overview of the current system may clear up some of the questions. The original design goal of ROS was to support large scientific and engineering applications without the traditional limitations of system architecture such as address space or the artificial limitations due to multi-user considerations such as memory partitioning. With this in mind, the minimum configuration for a Ridge two years ago was 2Mbytes of main memory. This allowed the expected performance (~780 speeds) to be achieved for single, large processes. What we found, however, was that the average customer would run not only a single large application, but would simultaneously run editors, compilers, and other such utility programs. Under this environment the very design advantages of ROS towards large applications, e.g., the ability for a process to allocate the entire set of system memory pages, became a hindrence to interactive processes while running a large cpu-bound process. This was usually because of excessive paging activity on machines configured with small amounts of memory. (Small, of course, being relative. Small on a Ridge is anything under 4Mbytes of memory, since the OS itself is using 1 to 1.5 Mbytes of memory.) The current Ridge's being delivered have a minimum of 4Mbytes of main memory. This configuration gives good performance for 2 to 6 users, depending of course on the exact mix of system activity. Adding more memory increases the multi-user capability of the current version of ROS simply by allowing more processes to run concurrently with a minimum of paging activity. The next version of ROS will greatly enhance the multi-user capabilities of the system by introducing a new virtual memory allocation algorithm. Essentially the new system now keeps two "classes" of memory pages; interactive and batch. The current released scheme is to treat all physical memory pages as equals, with the net effect that the virtual memory manager, VMM, will start paging out anybody to find free memory without giving any priority to "interactive" processes. With the new VMM, the "batch" page pool is searched first when attempting to allocate memory pages, thus giving the effect of increasing the "memory residency" of so-called interactive processes. This version of ROS is currently in beta test at several customers. Current plans call for the enhanced multi-user capabilities to be included at next patch level, which is expected shortly. For direct discussion/questions/opinions: - Doug Klein uucp: ...ridge!klein real: Ridge Computers 2451 Mission College Blvd Santa Clara, CA 95054 (408) 986-8500