"Instrumenting a running kernel for debugging or profiling is on
the wish list of many administrators and developers. Advocates of
OpenSolaris like to point to DTrace as a feature that Linux lacks,
though SystemTap has started to close that gap. The Linux Trace
Toolkit next generation (LTTng) takes a different approach and was
recently submitted for inclusion in the kernel (in two patches:
architecture independent and architecture dependent).
"LTTng relies upon kernel markers to provide static probe points
for its kernel tracing activities..."