In a simple test, for example, on fnpcc, I ran a couple of copies of
tiny ( unoptimized to make it run longer ).
Both copies reported the same time, but 'time' and 'top' showed the
second one running entirely in 'system' mode.
PCC > time ./tiny0 > /dev/null & ; time ./tiny0 > /dev/null & ;
[1] 21225
[2] 21226
PCC >
[2] Done ./tiny0 > /dev/null
4.850u 0.740s 0:05.87 95.2% 0+0k 0+0io 86pf+0w
[1] + Done ./tiny0 > /dev/null
0.730u 4.840s 0:05.56 100.1% 0+0k 0+0io 86pf+0w