On Tue, Aug 30, 2016 at 10:16:47PM -0400, Steven Rostedt wrote: > On Wed, 31 Aug 2016 11:11:38 +0900 > Namhyung Kim <namhy...@kernel.org> wrote: > > > On Tue, Aug 30, 2016 at 10:34:41AM +0900, Namhyung Kim wrote: > > > 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 <namhy...@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? > > > > On second thought, I think I can do it by just adding value of subtime > > to ftrace_graph_ret.calltime when graph-time is off. Then the > > calltime would not be the timestamp at function entry, but it seems > > not guaranteed due to the sleep-time anyway. Now I wonder why it > > doesn't have 'duration' in the ftrace_graph_ret instead of having > > calltime and rettime. > > > > As it hasn't worked, like forever, I'm thinking of nuking it. Nobody > seemed to have noticed. I haven't needed to use it, and apparently > nobody else has either. Why support a feature that nobody uses? > > I have used it for profiling, but not normal function graph tracing. > You can see the function times inside and do the logic post processing. > > Best bet is to just update the documentation to what the current code > does.
Ok, will send v2. Thanks, Namhyung
