Benchmarking mpsafevfs with parallel tarball extraction
http://lists.freebsd.org/pipermail/freebsd-smp/2005-May/000792.html

> Kernel was built without INVARIANTS and other debugging options,
> without ADAPTIVE_GIANT (which causes about a 200% performance penalty
> on system time in my testing, and has marginal impact on real or user
> time)

options ADAPTIVE_GIANT # Giant mutex is adaptive.

は、ないほうがいいのかしら。