Linux Trace Toolkit Quickstart
Author : Mathieu Desnoyers, September 2005
Last update : January 9th, 2009
This document is made of four parts : the first one explains how to install
LTTng and LTTV from Debian and RPM binary packages, the second one explains how
to install LTTng and LTTV from sources and the third one describes the steps
to follow to trace a system and view it. The fourth and last part explains
briefly how to add a new trace point to the kernel and to user space
applications.
What you will typically want is to read sections 2 and 3 : install LTTng from
sources and use it.
These operations are made for installing the LTTng 0.74 tracer on a linux 2.6.X
kernel. You will also find instructions for installation of LTTV 0.12.x : the
Linux Trace Toolkit Viewer.
To see the list of compatibilities between LTTng, ltt-control, LTTV and
markers-userspace, please refer to :
LTTng+LTTV versions compatibility
The following lttng patch is necessary to have the tracing hooks in the kernel.
The following ltt-control module controls the tracing.
Required programs and libraries are assumed to be automatically installed in an
installation with Debian or RPM packages. In the case of an installation from
sources, the dependencies are listed.
** Current development status **
LTTng :
Supported architectures :
x86 32/64 bits
PowerPC 32 and 64 bits
ARM (with limited timestamping precision, e.g. 1HZ. Need
architecture-specific support for better precision)
MIPS
LTTV :
supported architectures :
Intel 32/64 bits
PowerPC 32 and 64 bits
Possibly others. Takes care of endianness and type size difference between
the LTTng traces and the LTTV analysis tool.
***********************************************************
** Section 1 * Installation from Debian or RPM packages **
***********************************************************
* Create custom LTTV Debian packages
Use : dpkg-buildpackage -rfakeroot
You should then have your LTTV .deb files created for your architecture.
* Create custom LTTng packages
For building LTTng Debian packages :
Get the build tree with patches applies as explained in section 2.
make menuconfig (or xconfig or config) (customize your configuration)
make-kpkg kernel_image
You will then see your freshly created .deb in /usr/src. Install it with
dpkg -i /usr/src/(image-name).deb
Then, follow the section "Editing the system wide configuration" in section 2.
***********************************************************
** Section 2 * Installation from sources **
***********************************************************
* Prerequisites
Tools needed to follow the package download steps :
o wget
o bzip2
o gzip
o tar
You have to install the standard development libraries and programs necessary
to compile a kernel :
(from Documentation/Changes in the Linux kernel tree)
o Gnu C 2.95.3 # gcc --version
o Gnu make 3.79.1 # make --version
o binutils 2.12 # ld -v
o util-linux 2.10o # fdformat --version
o module-init-tools 0.9.10 # depmod -V
You might also want to have libncurses5 to have the text mode kernel
configuration menu, but there are alternatives.
Prerequisites for LTTV 0.x.x installation are :
gcc 3.2 or better
gtk 2.4 or better development libraries
(Debian : libgtk2.0, libgtk2.0-dev)
(Fedora : gtk2, gtk2-devel)
note : For Fedora users : this might require at least core 3 from Fedora,
or you might have to compile your own GTK2 library.
glib 2.4 or better development libraries
(Debian : libglib2.0-0, libglib2.0-dev)
(Fedora : glib2, glib2-devel)
libpopt development libraries
(Debian : libpopt0, libpopt-dev)
(Fedora : popt)
libpango development libraries
(Debian : libpango1.0, libpango1.0-dev)
(Fedora : pango, pango-devel)
libc6 development librairies
(Debian : libc6, libc6-dev)
(Fedora : glibc, glibc)
* Reminder
See the list of compatibilities between LTTng, ltt-control, LTTV and
markers-userspace at :
http://ltt.polymtl.ca > LTTng+LTTV versions compatibility
* Getting the LTTng packages
su -
mkdir /usr/src/lttng
cd /usr/src/lttng
(see http://ltt.polymtl.ca/lttng for package listing)
wget http://ltt.polymtl.ca/lttng/patch-2.6.X-lttng-0.x.xx.tar.bz2
bzip2 -cd patch-2.6.X-lttng-0.x.xx.tar.bz2 | tar xvof -
* Getting LTTng kernel sources
su -
cd /usr/src
wget http://kernel.org/pub/linux/kernel/v2.6/linux-2.6.X.tar.bz2
bzip2 -cd linux-2.6.X.tar.bz2 | tar xvof -
cd linux-2.6.X
- For LTTng 0.9.4- cat /usr/src/lttng/patch*-2.6.X-lttng-0.x.xx* | patch -p1
- For LTTng 0.9.5+ apply the patches in the order specified in the series file,
or use quilt
cd ..
mv linux-2.6.X linux-2.6.X-lttng-0.x.xx
* Installing a LTTng kernel
su -
cd /usr/src/linux-2.6.X-lttng-0.x.xx
make menuconfig (or make xconfig or make config)
Select the < Help > button if you are not familiar with kernel
configuration.
Items preceded by [*] means they has to be built into the kernel.
Items preceded by [M] means they has to be built as modules.
Items preceded by [ ] means they should be removed.
go to the "General setup" section
Select the following options :
[*] Prompt for development and/or incomplete code/drivers
[*] Activate markers
[*] Activate userspace markers ABI (experimental, optional)
[*] Immediate value optimization (optional)
[*] Linux Trace Toolkit Next Generation (LTTng) --->
or <*> Compile lttng tracing probes
or <*> Linux Trace Toolkit High-speed Lockless Data Relay
or <*> Linux Trace Toolkit Lock-Protected Data Relay
or <*> Linux Trace Toolkit Serializer
or <*> Linux Trace Toolkit Marker Control
or <*> Linux Trace Toolkit Tracer
[*] Align Linux Trace Toolkit Traces
or <*> Support logging events from userspace
[*] Support trace extraction from crash dump
or <*> Linux Trace Toolkit Trace Controller
or <*> Linux Trace Toolkit State Dump
Select
Select
Select
make
make modules_install
(if necessary, create a initrd with mkinitrd or your preferate alternative)
(mkinitrd -o /boot/initrd.img-2.6.X-lttng-0.x.xx 2.6.X-lttng-0.x.xx)
-- on X86, X86_64
make install
reboot
Select the Linux 2.6.X-lttng-0.x.xx kernel in your boot loader.
-- on PowerPC
cp vmlinux.strip /boot/vmlinux-2.6.X-lttng-0.x.xx
cp System.map /boot/System.map-2.6.X-lttng-0.x.xx
cp .config /boot/config-2.6.X-lttng-0.x.xx
depmod -ae -F /boot/System.map-2.6.X-lttng-0.x.xx 2.6.X-lttng-0.x.xx
mkinitrd /boot/initrd.img-2.6.X-lttng-0.x.xx 2.6.X-lttng-0.x.xx
(edit /etc/yaboot.conf to add a new entry pointing to your kernel : the entry
that comes first is the default kernel)
ybin
select the right entry at the yaboot prompt (see choices : tab, select : type
the kernel name followed by enter)
Select the Linux 2.6.X-lttng-0.x.xx kernel in your boot loader.
--
* Editing the system wide configuration
You must activate debugfs and specify a mount point. This is typically done in
fstab such that it happens at boot time.
If you have never used DebugFS before, these operation would do this for you :
mkdir /mnt/debugfs
cp /etc/fstab /etc/fstab.lttng.bkp
echo "debugfs /mnt/debugfs debugfs rw 0 0" >> /etc/fstab
then, rebooting or issuing the following command will activate debugfs :
mount /mnt/debugfs
You need to load the LTT modules to be able to control tracing from user
space. This is done by issuing the following commands. Note however
these commands load all LTT modules. Depending on what options you chose to
compile statically, you may not need to issue all these commands.
modprobe ltt-trace-control
modprobe ltt-marker-control
modprobe ltt-tracer
modprobe ltt-serialize
modprobe ltt-relay
modprobe ipc-trace
modprobe kernel-trace
modprobe mm-trace
modprobe net-trace
modprobe fs-trace
modprobe jbd2-trace
modprobe ext4-trace
modprobe syscall-trace
modprobe trap-trace
#if locking tracing is wanted, uncomment the following
#modprobe lockdep-trace
If you want to have complete information about the kernel state (including all
the process names), you need to load the ltt-statedump module. This is done by
issuing the command :
modprobe ltt-statedump
You can automate at boot time loading the ltt-control module by :
cp /etc/modules /etc/modules.bkp
echo ltt-trace-control >> /etc/modules
echo ltt-marker-control >> /etc/modules
echo ltt-tracer >> /etc/modules
echo ltt-serialize >> /etc/modules
echo ltt-relay >> /etc/modules
echo ipc-trace >> /etc/modules
echo kernel-trace >> /etc/modules
echo mm-trace >> /etc/modules
echo net-trace >> /etc/modules
echo fs-trace >> /etc/modules
echo jbd2-trace >> /etc/modules
echo ext4-trace >> /etc/modules
echo syscall-trace >> /etc/modules
echo trap-trace >> /etc/modules
#if locking tracing is wanted, uncomment the following
#echo lockdep-trace >> /etc/modules
* Getting and installing the ltt-control package (on the traced machine)
(note : the ltt-control package contains lttd and lttctl. Although it has the
same name as the ltt-control kernel module, they are *not* the same thing.)
su -
cd /usr/src
wget http://ltt.polymtl.ca/lttng/ltt-control-0.x-xxxx2006.tar.gz
gzip -cd ltt-control-0.x-xxxx2008.tar.gz | tar xvof -
cd ltt-control-0.x-xxxx2006
(refer to README to see the development libraries that must be installed on you
system)
./configure
make
make install
* Userspace tracing
Make sure you selected the kernel menuconfig option :
or <*> Support logging events from userspace
And that the ltt-userspace-event kernel module is loaded if selected as a
module.
Simple userspace tracing is available through
echo "some text to record" > /mnt/debugfs/ltt/write_event
It will appear in the trace under event :
channel : userspace
event name : event
* Getting and installing the LTTV package (on the visualisation machine, same or
different from the visualisation machine)
su -
cd /usr/src
wget http://ltt.polymtl.ca/packages/lttv-0.x.xx-xxxx2008.tar.gz
gzip -cd lttv-0.x.xx-xxxx2008.tar.gz | tar xvof -
cd lttv-0.x.xx-xxxx2008
(refer to README to see the development libraries that must be installed on your
system)
./configure
make
make install
* Getting and installing the markers-userspace package for user space tracing
(experimental)
See http://ltt.polymtl.ca/packages/markers-userspace-0.5.tar.bz2 or more recent.
***********************************************************
** Section 3 * Using LTTng and LTTV **
***********************************************************
* IMPORTANT : Arm Linux Kernel Markers after each boot
ltt-armall
* Use graphical LTTV to control tracing and analyse traces
lttv-gui (or /usr/local/bin/lttv-gui)
- Spot the "Tracing Control" icon : click on it
(it's a traffic light icon)
- enter the root password
- click "start"
- click "stop"
- Yes
* You should now see a trace
* Use text mode LTTng to control tracing
The tracing can be controlled from a terminal by using the lttctl command (as
root).
Start tracing :
lttctl -C -w /tmp/trace1 trace1
Stop tracing and destroy trace channels :
lttctl -D trace1
see lttctl --help for details.
(note : to see if the buffers has been filled, look at the dmesg output after
lttctl -R or after stopping tracing from the GUI, it will show an event lost
count. If it is the case, try using larger buffers. See lttctl --help to learn
how. lttv now also shows event lost messages in the console when loading a trace
with missing events or lost subbuffers.)
* Use text mode LTTV
Feel free to look in /usr/local/lib/lttv/plugins to see all the text and
graphical plugins available.
For example, a simple trace dump in text format is available with :
lttv -m textDump -t /tmp/trace
see lttv -m textDump --help for detailed command line options of textDump.
It is, in the current state of the project, very useful to use "grep" on the
text output to filter by specific event fields. You can later copy the timestamp
of the events to the clipboard and paste them in the GUI by clicking on the
bottom right label "Current time". Support for this type of filtering should
be added to the filter module soon.
* Hybrid mode
Starting from LTTng 0.5.105 and ltt-control 0.20, a new mode can be used :
hybrid. It can be especially useful when studying big workloads on a long period
of time.
When using this mode, the most important, low rate control information will be
recorded during all the trace by lttd (i.e. process creation/exit). The high
rate information (i.e. interrupt/traps/syscall entry/exit) will be kept in a
flight recorder buffer (now named flight-channelname_X).
The following lttctl commands take an hybrid trace :
Create trace channel, start lttd on normal channels, start tracing:
lttctl -C -w /tmp/trace2 -o channel.kernel.overwrite=1 trace2
Stop tracing, start lttd on flight recorder channels, destroy trace channels :
lttctl -D -w /tmp/trace2 trace2
Each "overwrite" channel is flight recorder channel.
* Flight recorder mode
The flight recorder mode writes data into overwritten buffers for all channels,
including control channels, except for the facilities tracefiles. It consists of
setting all channels to "overwrite".
The following lttctl commands take a flight recorder trace :
lttctl -C -w /tmp/trace3 -o channel.all.overwrite=1 trace3
...
lttctl -D -w /tmp/trace3 trace3
**************************************************************
** Section 4 * Adding new instrumentations with the markers **
**************************************************************
See Documentation/markers.txt and Documentation/tracepoints.txt in your kernel
tree.
* Add new events to userspace programs with userspace markers
http://ltt.polymtl.ca/packages/
Get the latest markers-userspace-*.tar.bz2 and see the Makefile and examples. It
allows inserting markers in executables and libraries, currently only on x86_32
and x86_64.