This enables the BPF Just in Time (JIT) compiler. BPF is a flexible and efficient infrastructure allowing to execute bytecode at various hook points. It is used in a number of Linux kernel subsystems such as networking (e.g. XDP, tc), tracing (e.g. kprobes, uprobes, tracepoints) and security (e.g. seccomp). LLVM has a BPF back end that can compile restricted C into a sequence of BPF instructions. After program load through bpf(2) and passing a verifier in the kernel, a JIT will then translate these BPF proglets into native CPU instructions. There are two flavors of JITs, the newer eBPF JIT currently supported on:
And the older cBPF JIT supported on the following archs:
eBPF JITs are a superset of cBPF JITs, meaning the kernel will migrate cBPF instructions into eBPF instructions and then JIT compile them transparently. Older cBPF JITs can only translate tcpdump filters, seccomp rules, etc, but not mentioned eBPF programs loaded through bpf(2).
Values : 0 - disable the JIT (default value) 1 - enable the JIT 2 - enable the JIT and ask the compiler to emit traces on kernel log.
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