Kernel Tracing: A Guide to Using Systemtap, Ftrace, and Perf for Linux Performance Optimization

Table of Contents

• Introduction
• Using Systemtap
• Using Ftrace
• Using Perf
• Conclusion

Introduction

Kernel tracing is an essential tool for developers and system administrators alike. It allows us to monitor and analyze the behaviour of the Linux kernel, helping us to diagnose and fix issues, optimize performance, and gain a deeper understanding of how the system works.

Using Systemtap

Systemtap is a powerful and flexible tool for kernel tracing that allows you to write scripts to monitor and analyze kernel behaviour. It can be used to trace a wide range of kernel events, from function calls and system calls to interrupts and network packets. Here’s an example of a simple systemtap script that traces all syscalls made by a specific process:

#!/usr/bin/env stap

probe syscall.* {
  if (pid() == target()) {
    printf("%s(%d) syscall: %s\n", execname(), pid(), probefunc())
  }
}

This script will print out the name of each syscall made by the process specified by the “target” variable.

Using Ftrace

Ftrace is a built-in tracing tool that comes with the Linux kernel. It can be used to trace a wide range of kernel events, from function calls and system calls to interrupts and network packets. Here’s an example of a simple ftrace command that traces all syscalls made by a specific process:

echo syscalls > /sys/kernel/debug/tracing/current_tracer
echo $$ > /sys/kernel/debug/tracing/set_ftrace_pid
cat /sys/kernel/debug/tracing/trace

This command will print out the name of each syscall made by the current process.

Using Perf

Perf is a powerful profiling tool that can be used for kernel tracing as well. It can be used to trace a wide range of kernel events, from function calls and system calls to interrupts and network packets. Here’s an example of a simple perf command that traces all syscalls made by a specific process:

perf record -e syscalls:sys_enter -a -g -p $$ sleep 1
perf report

This command will record all syscalls made by the current process for one second and then print out a report showing the frequency and duration of each syscall.

Conclusion

Kernel tracing is a powerful tool for diagnosing and optimizing Linux systems. Whether you prefer to use systemtap, ftrace, or perf, there are plenty of options available for tracing kernel events. By using these tools, you can gain a deeper understanding of how the kernel works and how to optimize your system for maximum performance.