> On Jul 27, 2016, at 8:53 PM, Steven Rostedt <[email protected]> wrote: > > I'm thinking you only need one tracepoint, and use function_graph > tracer for the length of the function call. > > # cd /sys/kernel/debug/tracing > # echo __alloc_pages_nodemask > set_ftrace_filter > # echo function_graph > current_tracer > # echo 1 > events/kmem/trace_mm_slowpath/enable
Thank you so much for your feedback! Actually, the goal is to only single out those cases with latencies higher than a given threshold. So, in accordance with this, I added those begin/end tracepoints and thought I could use a script to read the output of trace_pipe and only write to disk the trace information associated with latencies above the threshold. This would help prevent high disk I/O, especially when the threshold set is high. I looked at function graph trace, as you’d suggested. I saw that I could set a threshold there using tracing_thresh. But the problem was that slowpath trace information was printed for all the cases (even when __alloc_pages_nodemask latencies were below the threshold). Is there a way to print tracepoint information only when __alloc_pages_nodemask exceeds the threshold? Thanks! Janani. > > -- Steve > > >> return page; >> } >> >
