Hi Steven, On Tue, Jul 14, 2020 at 4:20 AM Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > You mean compared to non PREEMPT_RT_FULL of the same kernel? Yes. > I'd suggest trying 5.4 or even 5.6-rt. I tried 5.4.47-rt28, and the problem still persists. > Well, you could try: ftrace=function_graph ftrace_graph_filter workqueue_prepare_cpu > > If workqueue_prepare_cpu is a traceable function (not inlined nor notrace set). I tried "ftrace=function_graph ftrace_graph_filter=workqueue_prepare_cpu", however, the trace appears to be empty. The function workqueue_prepare_cpu is not defined inline nor notrace. Please see log below: # mount -t debugfs none /sys/kernel/debug # cd /sys/kernel/debug/tracing/ # cat trace # tracer: function_graph # # CPU DURATION FUNCTION CALLS # | | | | | | | # cat set_graph_function workqueue_prepare_cpu # cat tracing_on 1 Do you have any idea why it's empty? Thank you, Itai Handler
