[PATCH 6/6] Documentation: tracing: Add the startup timing of boot-time tracing
From: Masami Hiramatsu <mhiramat@kernel.org>
Date: 2020-09-10 12:44:06
Also in:
lkml
Subsystem:
documentation, the rest, tracing · Maintainers:
Jonathan Corbet, Linus Torvalds, Steven Rostedt, Masami Hiramatsu
Add the note about when to start the boot-time tracing. This will be needed for the people who wants to trace earlier boot sequence. Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> --- Documentation/trace/boottime-trace.rst | 14 ++++++++++++++ 1 file changed, 14 insertions(+)
diff --git a/Documentation/trace/boottime-trace.rst b/Documentation/trace/boottime-trace.rst
index c216f5695ae2..3931b43f902c 100644
--- a/Documentation/trace/boottime-trace.rst
+++ b/Documentation/trace/boottime-trace.rst@@ -120,6 +120,20 @@ instance node, but those are also visible from other instances. So please take care for event name conflict. +When to Start +============= + +All boot-time tracing options starting with ``ftrace`` will be enabled at the +end of core_initcall. This means you can trace the events from postcore_initcall. +Most of the subsystems and architecture dependent drivers will be initialized +after that (arch_initcall or subsys_initcall). Thus, you can trace those with +boot-time tracing. +If you want to trace events before core_initcall, you can use the options +starting with ``kernel``. Some of them will be enabled eariler than the initcall +processing (for example,. ``kernel.ftrace=function`` and ``kernel.trace_event`` +will start before the initcall.) + + Examples ========