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SubjectRe: [PATCH] ftrace: Access ret_stack->subtime only in the function profiler
Hi Steve,

On Mon, Aug 29, 2016 at 04:07:00PM -0400, Steven Rostedt wrote:
> On Mon, 29 Aug 2016 12:05:18 +0900
> Namhyung Kim <namhyung@kernel.org> wrote:
>
> > The subtime is used only for function profiler with function graph
> > tracer enabled. Move the definition of subtime under
> > CONFIG_FUNCTION_PROFILER to reduce the memory usage. Also move the
> > initialization of subtime into the graph entry callback.
>
> Hmm, I think documentation needs to be updated. Although it was never
> implemented, I believe I added the subtime to not only work with the
> profiler, but also with the normal tracing (to have the time of the
> internal functions subtracted from the upper level functions). But it
> appears that part was never implemented.
>
> I'm fine with the patch, or actually implementing what graph-time
> states in Documentation/ftrace.txt. If we take this patch, that comment
> needs to be made to only mention the profiler (and the option should
> only be shown when the profiler is enabled).

Ah, missed the documentation part. To implement it in the normal
tracing, I think we need to add 'subtime' field to struct
ftrace_graph_ret which will increase disk size. Are you ok with this?

Thanks,
Namhyung


>
> >
> > Cc: Josh Poimboeuf <jpoimboe@redhat.com>
> > Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> > ---
> > include/linux/ftrace.h | 2 ++
> > kernel/trace/ftrace.c | 6 ++++++
> > kernel/trace/trace_functions_graph.c | 1 -
> > 3 files changed, 8 insertions(+), 1 deletion(-)
> >
> > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> > index 6f93ac46e7f0..b3d34d3e0e7e 100644
> > --- a/include/linux/ftrace.h
> > +++ b/include/linux/ftrace.h
> > @@ -794,7 +794,9 @@ struct ftrace_ret_stack {
> > unsigned long ret;
> > unsigned long func;
> > unsigned long long calltime;
> > +#ifdef CONFIG_FUNCTION_PROFILER
> > unsigned long long subtime;
> > +#endif
> > #ifdef HAVE_FUNCTION_GRAPH_FP_TEST
> > unsigned long fp;
> > #endif
> > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> > index 84752c8e28b5..2050a7652a86 100644
> > --- a/kernel/trace/ftrace.c
> > +++ b/kernel/trace/ftrace.c
> > @@ -872,7 +872,13 @@ function_profile_call(unsigned long ip, unsigned long parent_ip,
> > #ifdef CONFIG_FUNCTION_GRAPH_TRACER
> > static int profile_graph_entry(struct ftrace_graph_ent *trace)
> > {
> > + int index = trace->depth;
> > +
> > function_profile_call(trace->func, 0, NULL, NULL);
> > +
> > + if (index >= 0 && index < FTRACE_RETFUNC_DEPTH)
> > + current->ret_stack[index].subtime = 0;
> > +
> > return 1;
> > }
> >
> > diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
> > index 0cbe38a844fa..9c7ffa4df5a8 100644
> > --- a/kernel/trace/trace_functions_graph.c
> > +++ b/kernel/trace/trace_functions_graph.c
> > @@ -170,7 +170,6 @@ ftrace_push_return_trace(unsigned long ret, unsigned long func, int *depth,
> > current->ret_stack[index].ret = ret;
> > current->ret_stack[index].func = func;
> > current->ret_stack[index].calltime = calltime;
> > - current->ret_stack[index].subtime = 0;
> > #ifdef HAVE_FUNCTION_GRAPH_FP_TEST
> > current->ret_stack[index].fp = frame_pointer;
> > #endif
>

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