The -Sfilename option to the RTS gives useful GC statistics, but it's hard to correlate these with other events, particularly to see if GC is interrupting critical sections in mutator threads. If the same information were instead logged via the eventlog system (perhaps enabled via a "-lg" option) one could get more insight into the garbage generation and collection behaviour of one's program.

Note that it's probably not necessary also to store the information given at the end of the run with both "-s" and "-S", though it may be interesting to contemplate moving this sort of thing into the eventlog file as well.