it's hard to say if this makes a measurable difference:
$ grep -C1 User.time timing-deepcopy.txt
Command being timed: "lilypond -I carver MSDM"
User time (seconds): 56.16
System time (seconds): 0.73
--
Command being timed: "./out/bin/lilypond.baseline -I carver MSDM"
User time (seconds): 56.50
System time (seconds): 0.76
--
Command being timed: "lilypond -I carver MSDM"
User time (seconds): 56.27
System time (seconds): 0.80
--
Command being timed: "./out/bin/lilypond.baseline -I carver MSDM"
User time (seconds): 56.13
System time (seconds): 0.73
--
Command being timed: "lilypond -I carver MSDM"
User time (seconds): 56.39
System time (seconds): 0.79
--
Command being timed: "./out/bin/lilypond.baseline -I carver MSDM"
User time (seconds): 56.28
System time (seconds): 0.68
https://codereview.appspot.com/561640045/
