Operating System Debugging

Debugging is the activity of finding and fixing errors in a system, both in hardware and in software.

Debugging can also include performance tuning, which seeks to improve performance by removing processing bottlenecks(points in a system or process where the flow or speed of movement is limited or constrained).

Failure Analysis

If a process fails, operating systems write the error information to a log file to alert system operators or users that the problem occurred. The operating system can also take a capture of the memory of the process and store it in a file for later analysis.

A failure in the kernel is called a crash. When a crash occurs, error information is saved to a log file, and the memory state is saved to a crash dump.

Note: Operating-system debugging and process debugging frequently use different tools and techniques due to the very different nature of these two tasks.

If in the file-system code kernel failure occurs then the kernel should try to save the state of the file on the file system before rebooting.

Performance Tuning

Performance tuning seeks to improve performance by removing processing bottlenecks. To identify bottlenecks, we monitor system performance.

Approach for Performance Tuning

The operating system has means of computing and displaying measures of system behavior. In a number of systems, the operating system produces trace listings of system behavior. All interesting events are logged with their time and important parameters and are written to a file. Later, an analysis program can process the log file to determine system performance and identify bottlenecks and inefficiencies. These traces can be run as input for a simulation of a suggested improved system. Traces also can help people operating systemfind errors in operating-system behavior.

Another Approach to Performance Tuning

Performance tuning uses single-purpose, interactive tools that allow users and administrators to question the state of various system components to look for bottlenecks.

The Windows Task Manager is a similar tool for Windows systems. The task manager includes information for current applications as well as processes, CPU and memory usage, and networking statistics.

DTrace

DTrace is a facility that dynamically adds probes(can refer to various techniques or tools used to monitor and gather information about the behavior, performance, or state of the operating system and the hardware it runs on. ) to a running system, both in user processes and in the kernel. These probes can be queried via the D programming language to determine an astonishing amount about the kernel, the system state, and process activities. For example, CPUs have a breakpoint feature that will halt execution and allow a debugger to examine the state of the system. Then execution can continue until the next breakpoint or termination. This method cannot be used in a multiuser operating-system kernel without negatively affecting all of the users on the system.

Operating system does the task by Profiling. Profiling, which periodically samples the instruction pointer to determine which code is being executed, can show statistical trends but not individual activities. Code can be included in the kernel to emit specific data under specific circumstances, but that code slows down the kernel and tends not to be included in the part of the kernel where the specific problem being debugged is occurring.

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