eBPF Practical Tutorial: Using eBPF to Trace Go Routine States

Go's concurrency model is a key feature that makes it stand out, with goroutines being lightweight, managed threads that make it easy to write concurrent programs. However, understanding and tracing the execution states of goroutines in real time can be challenging, especially when debugging complex systems. eBPF, a technology originally designed for network packet filtering, has evolved into a powerful tool for tracing and monitoring system behavior. By leveraging eBPF, developers can tap into the kernel and gather insights about the runtime behavior of Go programs, including the states of goroutines. Goroutines can switch states, such as RUNNABLE, RUNNING, WAITING, and DEAD, and understanding these states and how goroutines transition between them is crucial for diagnosing performance issues. eBPF allows developers to run custom programs inside the Linux kernel without changing the kernel source code or loading kernel modules. The eBPF kernel code that makes tracing goroutine states possible involves defining a ring buffer map to store goroutine execution data and attaching an uprobes to the runtime.casgstatus function in the Go program. The uprobes reads the goroutine ID from user space memory and stores the data in the ring buffer along with the process ID, thread group ID, and the new state of the goroutine. To run this tracing program, the eBPF code needs to be compiled and loaded by an eBPF loader. The program will output the state transitions of goroutines along with their goid, pid, and tgid. Tracing goroutine states using eBPF provides deep insights into the execution of Go programs, especially in production environments where traditional debugging tools may fall short. However, the offsets used in this eBPF program are specific to the Go version and the program being traced, and may change as Go evolves. In future explorations, this approach can be extended to trace other aspects of Go programs or even other languages, demonstrating the versatility and power of eBPF in modern software development.