> On Oct 21, 2016, at 3:08 AM, Michal Hocko <mho...@kernel.org> wrote: > > Interesting. > $ cat /debug/tracing/available_tracers > function_graph preemptirqsoff preemptoff irqsoff function nop > > Do I have to configure anything specially? And if I do why isn't it any > better to simply add a start tracepoint and make this available also to > older kernels?
Well, you just need to enable the function_graph tracer in the tracing directory: echo function_graph > current_tracer, set funcgraph-proc in trace_options to get process information: echo funcgraph-proc > trace_options, set funcgraph-abstime in trace_options to get timestamp, echo funcgraph-abstime > trace_options set all the functions we’d like to observe as filters. For e.g. echo __alloc_pages_nodemask > set_ftrace_filter and enable the tracepoints we would like to get information from. I didn’t add a begin tracepoint for this as Steven Rostedt had suggested using function graph instead of begin/end tracepoints (we already have a tracepoint in __alloc_pages_nodemask - trace_mm_page_alloc to get some information about the allocation and we can just use function graph to see how long __alloc_pages_nodemask() takes). Janani > -- > Michal Hocko > SUSE Labs
