Ftrace (Function Tracer) is the official, built-in tracing framework framework for the Linux kernel designed to help system engineers and developers analyze kernel behavior, profile performance, and debug latency spikes. Created by Steven Rostedt and integrated into Linux in 2008, it allows you to see exactly what functions the kernel is executing in real time without needing to install external tools. How Ftrace Works Internally
Ftrace uses dynamic tracing to monitor code execution with incredibly low performance overhead.
Compile-Time Space: When the Linux kernel is compiled, the compiler leaves blank placeholders (NOP instructions) at the beginning of every kernel function.
Dynamic Replacement: When you activate Ftrace, the kernel dynamically replaces those blank spaces with execution hooks to record data into a high-speed, lockless RAM ring buffer.
Zero Overhead When Off: When tracing is turned off, the hooks turn back into NOPs, meaning your system runs at native speed. The File System Interface (tracefs)
Ftrace does not rely on complex commands or graphical user interfaces. Instead, it exposes its configuration entirely through files inside a pseudo-filesystem. You configure it simply by reading (cat) and writing (echo) to specific files inside the /sys/kernel/tracing/ directory. Key files you interact with include: ftrace: trace your kernel functions! – Julia Evans
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