This document is made of five parts : the first one explains how to install LTTng and LTTV from sources, the second one describes the steps to follow to trace a system and view it. The third part explains briefly how to add a new trace point to the kernel and to user space applications. The fourth and last part explains how to create Debian or RPM packages from the LTTng and LTTV sources.
These operations are made for installing the LTTng 0.86 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, please
refer to :
LTTng+LTTV versions compatibility
The ongoing work had the Linux Kernel Markers integrated in the mainline Linux
kernel since Linux 2.6.24 and the Tracepoints since 2.6.28. In its current
state, the lttng patchset is necessary to have the trace clocksource, the
instrumentation and the LTTng high-speed data extraction mechanism added to the
kernel.
LTTng, UST and LTTV are developed by an open community. LTTng is released under a dual Gnu LGPLv2.1/GPLv2 license, except for very few kernel-specific files which are derived work from the Linux kernel.
LTTV is available under the Gnu GPLv2. The low-level LTTV trace reading library is released under Gnu LGPLv2.1.
The UST (Userspace Tracing) and the Userspace RCU libraries are released under the LGPLv2.1 license, which allows linking with non-GPL (BSD, proprietary...) applications. The associated headers are released under MIT-style/BSD-style licenses.
Please refer to each particular file licensing for details.
Tools needed to follow the package download steps :
You have to install the standard development libraries and programs necessary to compile a kernel :
(from Documentation/Changes in the Linux kernel tree) Gnu C 2.95.3 # gcc --version Gnu make 3.79.1 # make --version binutils 2.12 # ld -v util-linux 2.10o # fdformat --version 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)
See the list of compatibilities between LTTng, ltt-control and LTTV at : LTTng+LTTV versions compatibility.
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 -
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
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.
--
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
(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 # (run ldconfig to ensure new shared objects are taken into account) ldconfig
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
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 # (run ldconfig to ensure new shared objects are taken into account) ldconfig
ltt-armall
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
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 -D 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.)
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.
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.
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
See Documentation/markers.txt and Documentation/trace/tracepoints.txt in your kernel tree.
Also see ltt/probes/ for LTTng probe examples.
Note that a new design document for a 3rd generation of tracepoint/marker-based userspace tracing is available at LTTng User-space Tracing Design. This new infrastructure is not yet implemented.
The easy quick-and-dirty way to perform userspace tracing is currently to write an string to /mnt/debugfs/ltt/write_event. See Userspace tracing in the installation for sources section of this document.
Use : dpkg-buildpackage -rfakeroot
You should then have your LTTV .deb files created for your architecture.
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.