----- On Sep 1, 2020, at 5:13 AM, 熊毓华 <xiongyuhua@zju.edu.cn> wrote:

Hi，dear


Hello, I have encountered some problems in using LTTNG, which is briefly described as follows. I am eager to get your help.


About the use of the untrack command.It is reproduced as follows:

I type the following commands in turn to start LTTNG, and set up not to monitor a particular process.(For example, I input the "top" command in the terminal, the PID of the "top" process is 72598, now I want LTTNG not to monitor the "top" process)


  1. lttng create my-kernel-session --output=/tmp/my-kernel-trace
  2. lttng add-context -k -t pid
  3. lttng add-context -k -t tid
  4. lttng enable-event --kernel --all
  5. lttng untrack --kernel --pid=72598
  6. lttng start
  7. lttng destroy
  8. babeltrace2 /tmp/my-kernel-trace > babeltrace.txt


Unfortunately, the output still contains the data for PID72598.
Even after I changed "lttng untrack --kernel -- PID =72598" to "LTTNG untrack-u -- PID =72598", this phenomenon still occurred.

How do I use the lttng-untrack command to achieve my goal?


Based on the lttng-track(1) man page:

       The lttng track commands adds one or more values to a process attribute
       tracker.

       A process attribute tracker is an inclusion set of process attributes.
       Tracked processes are allowed to emit events, provided those events are
       targeted by enabled event rules (see lttng-enable-event(1)).

       Tracker values can be removed from an inclusion set with lttng-
       untrack(1).

What you are looking for is a an "exclusion set", which does not exist at this point
in LTTng.

Thanks,

Mathieu



Looking forward to your reply.
thanks,
yuhua

------------------
Yuhua Xiong
Lab for Internet and Security Technology
School of Computer Science and Technology
Zhejiang University
Hangzhou, 310007, P.R. China



--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com