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    Command:

    lttng

    
    
    
    

    SYNOPSIS

           lttng [OPTIONS] <COMMAND>
    
    
    

    DESCRIPTION

           The  LTTng project aims at providing highly efficient tracing tools for
           Linux.  It's tracers help tracking down performance issues  and  debug-
           ging  problems  involving  multiple  concurrent  processes and threads.
           Tracing across multiple systems is also possible.
    
           The lttng command line tool from the lttng-tools  package  is  used  to
           control both kernel and user-space tracing. Every interactions with the
           tracer should be done by this tool or by the liblttng-ctl provided with
           the lttng-tools package.
    
           LTTng  uses  a  session daemon (lttng-sessiond(8)), acting as a tracing
           registry, which permits you to interact with multiple  tracers  (kernel
           and  user-space)  inside  the same container, a tracing session. Traces
           can be  gathered  from  the  kernel  and/or  instrumented  applications
           (lttng-ust(3)).  Aggregating and reading those traces is done using the
           babeltrace(1) text viewer.
    
           In order to trace the kernel, the session daemon needs to be running as
           root.   LTTng  provides  the use of a tracing group (default: tracing).
           Whomever is in that group can interact with the root session daemon and
           thus  trace  the  kernel. Session daemons can co-exist meaning that you
           can have a session daemon running as Alice that can be  used  to  trace
           her applications along side with a root daemon or even a Bob daemon. We
           highly recommend to start the session daemon at boot  time  for  stable
           and long term tracing.
    
           Every  user-space  applications  instrumented  with  lttng-ust(3), will
           automatically register to the session daemon. This  feature  gives  you
           the ability to list available traceable applications and tracepoints on
           a per user basis. (See list command).
    
    
    

    OPTIONS

           This program follow the usual GNU command line syntax with long options
           starting  with two dashes. Below is a summary of the available options.
    
           -h, --help
                  Show summary of possible options and commands.
    
           -v, --verbose
                  Increase verbosity.  Three levels  of  verbosity  are  available
                  which  are  triggered by putting additional v to the option (-vv
                  or -vvv)
    
           -q, --quiet
                  Suppress all messages (even errors).
                  Simple listing of lttng commands.
    
    
    

    COMMANDS

           add-context
                  Add context to event(s) and/or channel(s).
    
                  A context is basically extra information appended to a channel or event. For
                  instance, you could ask the tracer to add the PID information within the
                  "sched_switch" kernel event. You can also add performance monitoring unit
                  counters (perf PMU) using the perf kernel API).
    
                  For example, this command will add the context information 'prio' and two perf
                  counters (hardware branch misses and cache misses), to all events in the trace
                  data output:
    
                  # lttng add-context -k -t prio -t perf:branch-misses -t perf:cache-misses
    
                  Please take a look at the help (-h/--help) for a detailed list of available
                  contexts.
    
                  If no channel and no event is given (-c/-e), the context is added to all
                  channels (which applies automatically to all events in that channel). Otherwise
                  the context will be added only to the channel (-c) and/or event (-e) indicated.
    
                  If -s, --session is omitted, the session name is taken from the .lttngrc
                  file.
    
                  OPTIONS:
    
                  -h, --help
                          Show summary of possible options and commands.
                  -s, --session NAME
                          Apply on session name.
                  -c, --channel NAME
                          Apply on channel name.
                  -e, --event NAME
                          Apply on event name.
                  -k, --kernel
                          Apply for the kernel tracer
                  -u, --userspace
                          Apply for the user-space tracer
                  -t, --type TYPE
                          Context type. You can repeat this option on the command line. Please
                          use "lttng add-context -h" to list all available types.
    
           calibrate
                  Quantify LTTng overhead
    
                  The LTTng calibrate command can be used to find out the combined average
                  an empty function, gathering PMU counters LLC (Last Level Cache) misses
                  information (see lttng add-context --help to see the list of available PMU
                  counters).
    
                  # lttng create calibrate-function
                  # lttng enable-event calibrate --kernel --function lttng_calibrate_kretprobe
                  # lttng add-context --kernel -t perf:LLC-load-misses -t perf:LLC-store-misses \
                                    -t perf:LLC-prefetch-misses
                  # lttng start
                  # for a in $(seq 1 10); do \
                          lttng calibrate --kernel --function;
                    done
                  # lttng destroy
                  # babeltrace $(ls -1drt ~/lttng-traces/calibrate-function-* | tail -n 1)
    
                  The output from babeltrace can be saved to a text file and opened in a
                  spreadsheet (e.g. oocalc) to focus on the per-PMU counter delta between
                  consecutive "calibrate_entry" and "calibrate_return" events. Note that these
                  counters are per-CPU, so scheduling events would need to be present to account
                  for migration between CPU. Therefore, for calibration purposes, only events
                  staying on the same CPU must be considered.
    
                  The average result, for the i7, on 10 samples:
    
                                            Average     Std.Dev.
                  perf_LLC_load_misses:       5.0       0.577
                  perf_LLC_store_misses:      1.6       0.516
                  perf_LLC_prefetch_misses:   9.0      14.742
    
                  As we can notice, the load and store misses are relatively stable across runs
                  (their standard deviation is relatively low) compared to the prefetch misses.
                  We can conclude from this information that LLC load and store misses can be
                  accounted for quite precisely, but prefetches within a function seems to behave
                  too erratically (not much causality link between the code executed and the CPU
                  prefetch activity) to be accounted for.
    
                  OPTIONS:
    
                  -h, --help
                          Show summary of possible options and commands.
                  -k, --kernel
                          Apply for the kernel tracer
                  -u, --userspace
                          Apply for the user-space tracer
                  --function
                          Dynamic function entry/return probe (default)
    
           create [OPTIONS] [NAME]
                  Create tracing session.
    
                  -h, --help
                          Show summary of possible options and commands.
                  --list-options
                          Simple listing of options
                  -o, --output PATH
                          Specify output path for traces
    
           destroy [OPTIONS] [NAME]
                  Teardown tracing session
    
                  Free memory on the session daemon and tracer side. It's gone!
    
                  If NAME is omitted, the session name is taken from the .lttngrc file.
    
                  OPTIONS:
    
                  -h, --help
                          Show summary of possible options and commands.
                  --list-options
                          Simple listing of options
    
           enable-channel NAME[,NAME2,...] [-k|-u] [OPTIONS]
                  Enable tracing channel
    
                  To enable event, you must first enable a channel which contains event(s).
    
                  If -s, --session is omitted, the session name is taken from the .lttngrc
                  file.
    
                  OPTIONS:
    
                  -h, --help
                          Show this help
                  --list-options
                          Simple listing of options
                  -s, --session
                          Apply on session name
                  -k, --kernel
                          Apply to the kernel tracer
                  -u, --userspace
                          Apply to the user-space tracer
    
                  --discard
                          Discard event when subbuffers are full (default)
                  --overwrite
    
           enable-event NAME[,NAME2,...] [-k|-u] [OPTIONS]
                  Enable tracing event
    
                  A tracing event is always assigned to a channel. If -c, --channel is
                  omitted, a default channel named 'channel0' is created and the event is
                  added to it. For the user-space tracer, using -a, --all is the same as
                  using the wildcard "*".
    
                  If -s, --session is omitted, the session name is taken from the .lttngrc
                  file.
    
                  OPTIONS:
    
                  -h, --help
                          Show summary of possible options and commands.
                  --list-options
                          Simple listing of options
                  -s, --session
                          Apply on session name
                  -c, --channel
                          Apply on channel name
                  -a, --all
                          Enable all tracepoints and syscalls
                  -k, --kernel
                          Apply for the kernel tracer
                  -u, --userspace
                          Apply for the user-space tracer
    
                  --tracepoint
                          Tracepoint event (default)
                          - userspace tracer supports wildcards at end of string. Don't forget to
                          quote to deal with bash expansion.
                          e.g.:
                          "*"
                          "app_component:na*"
                  --loglevel
                          Tracepoint loglevel
                  --probe [addr | symbol | symbol+offset]
                          Dynamic probe. Addr and offset can be octal (0NNN...), decimal (NNN...)
                          or hexadecimal (0xNNN...)
                  --function [addr | symbol | symbol+offset]
                          Dynamic function entry/return probe. Addr and offset can be octal
                          (0NNN...), decimal (NNN...) or hexadecimal (0xNNN...)
                  --syscall
                          System call event
                          Enabling syscalls tracing (kernel tracer), you will not be able to disable them
                          with disable-event. This is a known limitation. You can disable the entire
                          channel to do the trick.
    
           disable-channel NAME[,NAME2,...] [-k|-u] [OPTIONS]
                  -s, --session
                          Apply on session name
                  -k, --kernel
                          Apply for the kernel tracer
                  -u, --userspace
                          Apply for the user-space tracer
    
           disable-event NAME[,NAME2,...] [-k|-u] [OPTIONS]
                  Disable tracing event
    
                  The event, once disabled, can be re-enabled by calling lttng enable-event
                  NAME again.
    
                  If -s, --session is omitted, the session name is taken from the .lttngrc
                  file.
    
                  OPTIONS:
    
                  -h, --help
                          Show summary of possible options and commands.
                  --list-options
                          Simple listing of options
                  -s, --session
                          Apply on session name
                  -k, --kernel
                          Apply for the kernel tracer
                  -u, --userspace
                          Apply for the user-space tracer
    
           list [-k|-u] [SESSION [SESSION_OPTIONS]]
                  List tracing session information.
    
                  With no arguments, it will list available tracing session(s).
    
                  With the session name, it will display the details of the session including
                  the trace file path, the associated channels and their state (activated
                  and deactivated), the activated events and more.
    
                  With -k alone, it will list all available kernel events (except the system
                  calls events).
                  With -u alone, it will list all available user-space events from registered
                  applications. Here is an example of 'lttng list -u':
    
                  PID: 7448 - Name: /tmp/lttng-ust/tests/hello/.libs/lt-hello
                        ust_tests_hello:tptest_sighandler (type: tracepoint)
                        ust_tests_hello:tptest (type: tracepoint)
    
                  You can now enable any event listed by using the name :
                  ust_tests_hello:tptest.
    
                  -d, --domain
                          List available domain(s)
    
           set-session NAME
                  Set current session name
    
                  Will change the session name in the .lttngrc file.
    
                  OPTIONS:
    
                  -h, --help
                          Show summary of possible options and commands.
                  --list-options
                          Simple listing of options
    
           start [OPTIONS] [NAME]
                  Start tracing
    
                  It will start tracing for all tracers for a specific tracing session.
    
                  If NAME is omitted, the session name is taken from the .lttngrc file.
    
                  OPTIONS:
    
                  -h, --help
                          Show summary of possible options and commands.
                  --list-options
                          Simple listing of options
    
           stop [OPTIONS] [NAME]
                  Stop tracing
    
                  It will stop tracing for all tracers for a specific tracing session.
    
                  If NAME is omitted, the session name is taken from the .lttngrc file.
    
                  OPTIONS:
    
                  -h, --help
                          Show summary of possible options and commands.
                  --list-options
                          Simple listing of options
    
           view [SESSION_NAME] [OPTIONS]
                  View traces of a tracing session
    
                  By default, the babeltrace viewer will be used for text viewing.
    
                  If SESSION_NAME is omitted, the session name is taken from the .lttngrc file.
    
                  OPTIONS:
    
                  -h, --help
                          Show this help
                  --list-options
                          Simple listing of options
                  -t, --trace-path PATH
                          Trace directory path for the viewer
                  -e, --viewer CMD
                          Specify viewer and/or options to use
                          This will completely override the default viewers so
                          please make sure to specify the full command. The trace
                          directory path of the session will be appended at the end
                          to the arguments
    
    
    

    EXIT VALUES

           0      Success
    
           1      Command error
    
           2      Undefined command
    
           3      Fatal error
    
           4      Command warning
    
           16     No session found by the name given
    
           18     Error in session creation
    
           21     Error in application(s) listing
    
           28     Session name already exists
    
    
           40     Kernel channel disable failed
    
           41     Kernel channel enable failed
    
           42     Kernel context failed
    
           43     Kernel enable event failed
    
           44     Kernel disable event failed
    
           53     Kernel listing events failed
    
           60     UST channel disable failed
    
           61     UST channel enable failed
    
           62     UST adding context failed
    
           63     UST event enable failed
    
           64     UST event disable failed
    
           66     UST start failed
    
           67     UST stop failed
    
           75     UST event exists
    
           76     UST event not found
    
           77     UST context exists
    
           78     UST invalid context
    
    
    
    

    ENVIRONMENT VARIABLES

           Note that all command line options override environment variables.
    
           LTTNG_SESSIOND_PATH
                  Allows  one  to  specify  the full session daemon binary path to
                  lttng command line tool. You can also use --sessiond-path option
                  having the same effect.
    
    
    

    SEE ALSO

           babeltrace(1), lttng-ust(3), lttng-sessiond(8)
    
    
    

    BUGS

           No show stopper bugs are known yet in this version.
    
           If  you  encounter any issues or usability problem, please report it on
           our mailing  list  <lttng-dev@lists.lttng.org>  to  help  improve  this
           project.
    
    
    

    CREDITS

           lttng  is  distributed  under the GNU General Public License version 2.
           See the file COPYING for details.
    
           A Web site is available at http://lttng.org for more information on the
           LTTng project.
    
           You can also find our git tree at http://git.lttng.org.
    
           Mailing lists for support and development: <lttng-dev@lists.lttng.org>.
    
           You can find us on IRC server irc.oftc.net (OFTC) in #lttng.
    
    
    

    THANKS

           Thanks to Yannick Brosseau without whom this project would  never  have
           been  so  lean  and  mean! Also thanks to the Ericsson teams working on
           tracing which helped us greatly with detailed bug reports  and  unusual
           test cases.
    
           Thanks  to our beloved packager Alexandre Montplaisir-Goncalves (Ubuntu
           and PPA maintainer) and Jon Bernard for our Debian packages.
    
           Special thanks to Michel Dagenais and the DORSAL  laboratory  at  Poly-
           technique de Montreal for the LTTng journey.
    
    
    

    AUTHORS

    
    
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