Kernel tracing technology – an overview
In order to trace or profile, a data source (or several) are required; the Linux kernel provides them, of course. Tracepoints are a primary data source within a kernel (in fact, we covered using the kernel's dynamic event tracing in Chapter 4, Debug via Instrumentation – Kprobes in the The easier way – dynamic kprobes or kprobe-based event tracing section). The kernel has several predefined tracepoints; you can see them here: /sys/kernel/tracing/events/. Many tracing tools rely on them. You can even set up tracepoints dynamically by writing to /sys/kernel/tracing/kprobe_events (we covered this too in Chapter 4, Debug via Instrumentation – Kprobes via dynamic kprobes, as just mentioned).
Other data sources include kprobes, uprobes (the equivalent of kprobes for userspace), USDT/dprobes and LTTng-ust (these latter two are for user mode tracing; also, LTTng has several kernel modules that it inserts into the...
