Here are results of a simple run (average of three results, bigger is better) of tools from unixbench suite with WITNESS+INVARIANTS enabled and disabled:
. |
aritoh |
float |
context1 |
syscall |
WITNESS+INVARIANTS |
76467098 |
7477383 |
66894 |
460400 |
Plain |
78024481 |
7549189 |
265514 |
1308646 |
This benchmark was performed on i386 Athlon64 1.6 GHz machine, on FreeBSD 6.1-RELEASE. There's no statistical analysis, but there's clearly an order-of-magnitude impact on some workloads.
WITNESS and INVARIANTS are debug options that should not be enabled on production systems.