The Profile Collection Toolkit (PCT) provides a novel generalized CPU
profiling facility.  PCT enables arbitrarily late profiling activation
and arbitrarily early report generation.  PCT usually requires no
re-compilation, re-linking, or even re-starting of programs.
Profiling reports gracefully degrade with available debugging data.

PCT uses its debugger controller, dbctl, to drive a debugger's control
over a process.  dbctl has a configuration language that allows users
to specify context-specific debugger commands.  These commands can
sample general program state, such as call stacks and function parameters.

For systems or situations with poor debugger support, PCT provides several
other portable and flexible collection methods.  PCT can track most program
code, including code in shared libraries and late-loaded shared objects.
On Linux, PCT can seamlessly merge kernel CPU time profiles with user-level
CPU profiles to create whole system reports.