Memory Usage in the LANL CM-5 Workload

It is generally agreed that memory requirements should be taken into account in the scheduling of parallel jobs. However, so far the work on combined processor and memory scheduling has not been based on detailed information and measurements. To rectify this problem, we present an analysis of memory usage by a production workload on a large parallel machine, the 1024-node CM-5 installed at Los Alamos National Lab. Our main observations are { The distribution of memory requests has strong discrete components, i.e. some sizes are much more popular than others. { Many jobs use a relatively small fraction of the memory available on each node, so there is some room for time slicing among several memory-resident jobs. { Larger jobs (using more nodes) tend to use more memory, but it is diicult to characterize the scaling of per-processor memory usage.