Extended Berkeley Packet Filter (eBPF) fundamentally changes how operators gain system-level insights into Linux kernels. Instead of modifying kernel code or compiling custom kernel modules, eBPF runs sandboxed programs directly inside the operating system core.
eBPF lets tracing tools run small programs inside the Linux kernel when selected events occur, such as a system call, a network packet arriving, or a function being entered. Instead of repeatedly asking the kernel for information from a separate monitoring process, the tool can collect or filter data close to where the event happens.
That placement is a major reason tracing can have low overhead. An eBPF program can discard irrelevant events in the kernel and send only useful results to a user-space application. It can also aggregate counts or latencies in eBPF maps, so the kernel does not need to send every event across the boundary.
Because the program is event-driven and can do its work in place, a trace can avoid some of the cost of frequent context switches and large volumes of data transfer. The verifier also helps make it practical to run tracing programs without loading arbitrary kernel code.
“Low overhead” does not mean no overhead. A hook that fires extremely often, a program that does too much work per event, or a trace that exports excessive data can still affect performance. Good eBPF tools keep handlers short, filter early, and measure the tracing cost under the workload they care about.
