On Fri, 21 Nov 2014 09:33:44 +0000 Markos Chandras <Markos.Chandras@xxxxxxxxxx> wrote: > Hi Steven, > > I had a look on > > https://www.kernel.org/doc/Documentation/trace/ftrace-design.txt > > and section "HAVE_FUNCTION_GRAPH_TRACER" > > According to the sample code, first we check "ftrace_trace_function != > ftrace_stub" and if that's true, then we never check the ftrace_graph_* > functions which is exactly what MIPS does. So the graph functions are > not always checked. x86 seems to do something similar in mcount_64.S > Thanks, I need to update that file. I don't test static tracing much as I feel it's overhead makes it almost not worth keeping. I've been even thinking of nuking it, but I keep it in because it's good for archs adding function tracing to get a basic test working, as dynamic function tracing is a bit more difficult to implement. But yeah, don't go too much by that document. It is out of date, and when I get time, I'll have to update it. I'll probably do that when I bring powerpc up to speed with x86 (except for the fentry part). I want dynamic trampolines for powerpc and such, and when I do that, it will make all the changes fresh in my mind to go back and tackle the design documentation. -- Steve
