X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=blobdiff_plain;f=doc%2Fquickstart.txt;h=163544eee1e23fd3aa0695e0db7b53644fa172c1;hp=d3fde8666bcace092fff082bec67c11f1ec7b6f5;hb=b79f82bbde7fd1fb50a6820d5ffabdbe105941ed;hpb=1aa502dd1ba0eb2f1936890e383f79cc97d349c2 diff --git a/doc/quickstart.txt b/doc/quickstart.txt index d3fde8666..163544eee 100644 --- a/doc/quickstart.txt +++ b/doc/quickstart.txt @@ -1,37 +1,48 @@ +NOTES: +-------------- +2011-07-21 : User-space tracer is not released. Tracing in user-space at this +point is not possible with lttng-tools. + QUICKSTART -------------- This is a quick start guide for the complete LTTng tool chain. This is divided -in three sections respectively Kernel tracing, user-space tracing and reading a +in three sections respectively kernel tracing, user-space tracing and reading a trace. See the README file for installation procedure or use the various Linux distribution packages. -In order to trace the Kernel, you'll need the lttng-modules >= 2.0 compiled and -installed. See http://lttng.org/content/lttng-kernel-tracer for more -instructions for that part. For user-space tracing, you'll need an instrumented -application, please see http://lttng.org/ust +In order to trace the kernel, you'll need the lttng-modules >= 2.0 compiled and +installed. See http://lttng.org/lttng2.0 for more instructions for that part. +For user-space tracing, you'll need an instrumented application, please see +http://lttng.org/ust. lttng-tools provide a session daemon (ltt-sessiond) that acts as a tracing registry. To trace any instrumented applications or the kernel, a registered -tracing session is needed. +tracing session is needed beforehand. To interact with the session daemon and a +tracing session, you should use the lttng command line UI (lttng). -To interact with the session daemon and a tracing session, you can use the -lttng command line UI (lttng). +Here is a list of some powerful features the LTTng 2.0 kernel tracer offers: + + * Kprobes support + * Function Tracer support + * Context information support (add context data to an event) + * Perf counter support + * Tracepoint support The next sections explain how to do tracing :) Kernel Tracing -------------- -You have to modprobe the lttng-modules manually or the session daemon will do -it for you if they can be found on your system. - -You can then start the session daemon by hand or the lttng command line tool -will do it for you. +You can start the session daemon by invoking the command "ltt-sessiond", +or let the lttng command line tool do it for you. The session daemon +loads the LTTng tracer modules for you if those modules can be found on +your system. If they are not found, the kernel tracing feature will be +unavailable. -List possible kernel events: +List available kernel events: # lttng list -k @@ -40,6 +51,10 @@ the session name (here 'mysession') you are working on. # lttng create mysession +If you have multiple sessions, you can change the current session by using + +# lttng set-session myothersession + 2) Enable event(s). Here for example, we want only 'sched_switch' and 'sys_enter' events for the kernel (-k/--kernel). @@ -49,21 +64,69 @@ or enable ALL events (-a/--all): # lttng enable-event -a -k -3) Start tracing: +3) Enable kprobes and/or the function tracer with lttng + +This is a new feature made possible by the new LTTng 2.0 kernel tracer. You can +enable a dynamic probe and data will be output in the trace along side with +your tracing data. + +# lttng enable-event aname --probe symbol+0xffff7260695 + +or + +# lttng enable-event aname --probe 0xffff7260695 + +Either an
or a can be used for probes. + +You can also enable function tracer, which uses the Ftrace API (by Steven +Rostedt). Again, data will be output in the trace. + +# lttng enable-event aname --function + +4) Enable context information for an event: + +This is also a new feature which allows you to add context information to an +event. For example, you can add the PID along with the event information: + +# lttng add-context -k -e sched_switch -t pid + +At this point, you will have to look at 'lttng add-context --help' for all +possible context type which are integer values. + +You can on the same line activate multiple context: + +# lttng add-context -k -e sched_switch -t pid -t nice -t tid + +5) Enable perf counter for an event: + +Again, a new powerful feature is the possibility to add perf counter data +(using the perf API by Ingo Molnar and Thomas Gleixner) to the trace on a per +event basis. Let say we want to get the CPU cycles at each event: + +# lttng add-context -k -e sched_switch -t perf:cpu-cycles + +You'll have to use the add-context help for all possible perf counter values. + +6) Start tracing: # lttng start -Tracing is in progress at this point and will be written in +Tracing is in progress at this point and traces will be written in $HOME/lttng-traces/mysession--