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Richard J Moore - IBM

TUTORIAL: Using SystemTap and kdump

In 2004 Linux took a major leap forward with the acceptance of kexec and kprobes into the base 2.6 kernel. These kernel extensions have enabled the creation of two very powerful system debugging facilities, which are part of all kernels from 2.6.13 on. They form the basis for doing production time debugging as well as being an invaluable aid to the developer.

It is often difficult to diagnose complex problems without multiple rebuilds and reboots. Even in a simple setup, the problem can touch various layers of the application and operating system. Diagnosis is even more difficult in complex, multi-tiered systems. As Linux is deployed in these environments, it is becoming more important to have facilities to locate and identify such problems.

Using the kprobes infrastructure, SystemTAP is being developed to dynamically instrument the kernel and user applications. SystemTAP instrumentation incurs low overhead when enabled, and zero overhead when disabled. SystemTAP provides facilities to define instrumentation points in a high-level language, and to aggregate and analyze the instrumentation data. Details of the SystemTAP architecture and implementation are presented, along with examples of solving problems in the production environments.

This introductory workshop is for those who are curious about how problems can be diagnosed using kdump and SystemTap. We will run through the set-up of each tool and demonstrate simple-yet-powerful debugging scenarios based upon their use. We will also cover some of the basic technical knowledge that underpins system debugging techniques.