Hi, Here are the test results using (ice-9 time) with the attached "time.scm" and guix/base16.scm, to be run with ‘make && ./pre-inst-env guix repl time.scm’: old: clock utime stime cutime cstime gctime 3.93 6.32 0.03 0.00 0.00 3.59 clock utime stime cutime cstime gctime 3.92 6.32 0.03 0.00 0.00 3.59 clock utime stime cutime cstime gctime 3.86 6.24 0.02 0.00 0.00 3.54 new: clock utime stime cutime cstime gctime 2.43 3.60 0.02 0.00 0.00 1.76 clock utime stime cutime cstime gctime 2.49 3.67 0.01 0.00 0.00 1.77 clock utime stime cutime cstime gctime 2.64 3.77 0.01 0.00 0.00 1.77 About half as much time is spent in GC. The ‘utime’ is also half as much. Not sure what ‘clock’ means exactly, but it is reduced as well. Greetings, Maxime