On Fri, Jan 17, 2020 at 10:52 AM Jerin Jacob <jerinjac...@gmail.com> wrote: > > > If someone needs more time to think through or any clarification is > > > required then please discuss. > > > > I did not find the time to look at this. > > Some quick questions: > > - is LTTng coming with out-of-tree kmod? making it hard to support in > > distributions? > > LTTng kernel tracing only needs kmod support. > For the userspace tracing at minium following libraries are required. > > a) LTTng-UST > b) LTTng-tools > c) liburcu > d) libpopt-dev > > Based on the https://lttng.org/docs/v2.11/#doc-installing-lttng > -------------------------- 8<---------------------------------- > Important:As of 22 October 2019, LTTng 2.11 is not available as > distribution packages, except for Arch Linux. > You can build LTTng 2.11 from source to install and use it. > -------------------------- >8----------------------------------
Would there be requirements on a specific version of LTTng? I can see RHEL 7 comes with version 2.4.1, RHEL 8 has 2.8.1. > > - I have been playing with perf those days to track live processes and > > gathering informations/stats at key point of a dpdk app without adding > > anything in the binary. What does LTTng provide that scripting around > > perf would not solve? > > Profiler and Tracer are two different things: Perf is a profiler. Are you sure you can draw such a line about perf? You can add dynamic tracepoints with context in a live process (perf probe/perf recordma), I used this to track where a variable was getting updated once for a given device in OVS (and getting the number of occurrences). I know there are limitations with perf (some static variables not being caught, can be tricky to trace inlines). Maybe LTTng is better at this since you put markers in your code. One thing of interest, I understand that LTTng does not require a context switch when tracing. That is an advantage over perf. -- David Marchand
