You can now time the execution of processing flows in Scons using a TIMER option. Use it like this:
scons TIMER=y <target>
An example from rsftour:



bash$ scons -Q TIMER=y windowed.rsf

/usr/bin/time < Txx.HH /path/to/RSF/bin/sfwindow n2=10 n1=200 f1=200 > windowed.rsf

0.00user 0.01system 0:00.00elapsed 0%CPU (0avgtext+0avgdata 0maxresident)k

0inputs+0outputs (170major+25minor)pagefaults 0swaps

Thanks to Jim Jennings for the idea.