DTrace is a dynamic tracing tool build by Sun Microsystems and is available for Solaris, MacOS and FreeBSD. It features a tracing language which can be used to probe certain “probing” points in kernel or userland. This can be very useful to gather statistics, etc. Linux comes with a separate solution called systemtap. It also features a tracing language and can probe both userland and kernel space. A few Linux distributions such as Fedora enable systemtap in their default kernel.