I'm not familar with accounting in a cluster, but you will need the usual system accounting installed on all the nodes.
The part I'm not familar with is collating all of the accounting reports from multiple nodes to get the resulting time spent. Using the base tools you would get a process accounting with the information, but each report would be for a node. This works if you don't have too many nodes... but once you pass about 10 it gets to be a real problem...
The reference in http://marc.info/?l=beowulf&m=99248650613978&w=2
is a bit dated, but it is the kind of thing you are looking for.