dhinds@portia.Stanford.EDU (David Hinds) (03/24/90)
We have an Iris 4D/240 system (4 processors), used for a combination of interactive graphics and computation-intensive molecular dynamics calculations. We've been trying to find a way of managing processes that will keep the machine fully utilized, but will still give reasonable responsiveness for interactive work. So far we have been unsuccessful. When all four processors are doing work (i.e., four batch jobs are running), it is impossible to even log on to the console. At first, we thought this was a memory problem, but we've upgraded to 32MB now, and this happens even when >4000 pages are free. The console lockup happens when all the batch processes are at maximum niceness (39), and still happens even when they are all set to a non-degrading priority of 128 with npri. As I understand it, at a priority of +128, these jobs should not get even a second of CPU time if there are other demands on the system. Interactive use on text-only terminals, however, seems normal under these load conditions - editing, compiling, etc don't seem any slower. I expect that logging on to the console is a fairly expensive process. But why is it so expensive that the system can't manage it in the presence of background work? It seems as if the console requires a CPU for itself just to run. Will this problem be corrected in the improved batch facilities in the next software release? -David Hinds dhinds@portia.stanford.edu