Oprofile

System-wide profiler
Use processor performance monitoring hardware
Relatively low overhead
Supports x86 processors (x86_64, ppc64, ia64, and Alpha being developed)
Good for finding hotspots and places where processor having problems
Two implementations, one for Linux 2.4 and another for Linux 2.5 kernels
- Red Hat 8.0 the Linux 2.4 interface
- Phoebe beta the backport of Linux 2.5 interface

System-wide profiler