A Source-level Kernel Profiler based on Dynamic Aspect-Orientation

We present a source-level kernel profiler named KLAS. Since this profiler is based on dynamic aspect-orientation, it allows the users to describe any code fragment in the C language. That code fragment is automatically executed for collecting detailed performance data at execution points specified by the users. Enabling dynamic aspect-orientation is crucial since otherwise the users would have to reboot an operating system kernel whenever they change aspects. Although KLAS dynamically transforms the binary of a running operating system kernel for weaving an aspect at runtime, unlike other similar tools, the KLAS users can specify those execution points, that is, joinpoints through a source-level view. For example, the users can describe a pointcut that picks up accesses to a member of a structure; they do not have to explicitly specify the addresses of the machine instructions corresponding to the member accesses. We have implemented this feature by extending a C compiler to produce augmented symbol information. KLAS has been implemented for the FreeBSD operating system with the GNU C compiler.