Improving boot performance with Bootchart
Shining Boot

© Markus Langer, Fotolia
Bootchart analyzes the boot process and tells you where the system is wasting time.
In this article, I explain how to deploy Bootchart to investigate the boot process and discover where system optimization can be applied to maximum effect.
One of the gripes about Linux is the amount of time it takes to boot. When you switch on a Linux-based mobile phone, you don't want to wait half an hour before you can start to use it. Linux desktop users aren't infinitely patient either, and developers have introduced various tools over the years to tackle the issue of boot time. If you make the effort to analyze the boot process, the results can be remarkable. The Moblin2 distribution boots from a solid-state drive in just five seconds [1], and the boot time for the usual Debian on an Asus Eee PC 901 can be reduced to a fast 14 seconds.
A handy tool called Bootchart [2] investigates the boot performance of a Linux computer. The application painstakingly logs the boot times for individual services and processes, then it converts the data into a lengthy Gantt diagram and outputs it in EPS, PNG, or SVG format. The diagram serves as a guide for directing your performance-tuning efforts.
Bootchart is installed easily on Ubuntu 8.10 and openSUSE 11 with the distribution's package. Packages are available for other distros, too. On openSUSE, you additionally need to add the init=/sbin/bootchartd option as a kernel parameter in your Grub boot menu (see the box titled "Bootchart for openSUSE 11").
Introducing Bootchart
Bootchart consists of a shell script that runs before the init process. The script calls init, then it starts logging data. Bootchart gleans information from the /proc directory or, to be more precise, /proc/stat, /proc/diskstats, and /proc/*/stat. (The asterisk is a wildcard that represents any process that binds /proc.)
Bootchart uses the virtual tmpfs filesystem to store the data in RAM initially: It stops collecting data when it sees the names of a couple of typical processes that occur when the login screen is displayed, such as gdmgreeter and kdm_greet. It then swaps the collection from RAM into the /var/log/bootchart.tgz file on your hard disk.
In Ubuntu, a Java application first automatically converts the data into a PNG graphic, which is stored in the /var/log/bootchart directory. In openSUSE 11, you need to enter the following at the command line to do the same thing:
$ sudo bootchart --format png
The graphic generated from the TGZ archive is then stored in the directory in which you issued the command.
Because the boot procedure is something like a race between dozens or hundreds of processes, the Bootchart graphic can be quite confusing. To make life easier for users, Bootchart comes with a tree-pruning function that lets you hide inactive and very short lived processes. Also, you can group similar processes for easier viewing.
Bootgraph
Before you start your analysis, hand over the stage to Bootgraph, a utility that comes from the Linux kernel developers. Bootgraph is included with the kernel scripts starting with version 2.6.28. In combination with a simple Perl script, Bootgraph shows what the Linux kernel does at boot time, and it offers a couple of optimization options.
To use Bootgraph, you first need to type uname -r to find out whether your kernel version is 2.6.28 or later. If so, reboot your system and add a new kernel parameter, initcall_debug, to the Grub boot manager, as described in the "Bootchart for openSUSE 11" box.
Now reboot your computer with the new option enabled and type the following simple command to create a vector graphic:
$ dmesg | perl /usr/src/kernel/scripts/bootgraph.pl > /home/User/bootgraph.svg
This command uses a Perl script to dissect the output from dmesg and store the results – an SVG-formatted graphic – in the home directory for the user. To view the graphic (Figure 1), use the Firefox browser – although this gives you a landscape view – or use a vector drawing program like Inkscape to rotate it 90 degrees.

Bootchart for openSUSE 11
OpenSUSE 11 offers two approaches to specifying additional boot parameters: Either you can enter them permanently in the /boot/grub/menu.lst file – you need to add them to the line starting with kernel in the section for your current distribution – or you can type the line directly in the Grub boot menu to run it once. To enter the information in the Grub boot menu, use the arrow keys to move to the right boot entry, and press E to edit. Then add init=/sbin/bootchartd to the end of the line starting with kernel.Pressing Enter confirms the change, and pressing B will boot your machine with the modified line.
Seeing is Believing
At the top of the Bootchart-generated diagram (Figure 2) are various statistics that give you the date of the test, the name of your Linux distribution, and your kernel version. Below this, you will see details of your CPU and the enabled kernel options. The time that elapses during the boot phase is listed next to the time keyword.

The two diagrams that follow show the CPU load during the boot phase and the input/output activity. Valleys represent idle processor time. Because the diagram shares the X axis with the main chart, you can also see which processes are not stressing the CPU sufficiently and thus are wasting valuable boot time. The next diagram looks similar but relates to the hard disk, showing the data throughput and active time for the disk.
The main part of the Bootchart graphic starts below this. The X axis represents the number of seconds that elapse during the boot process. For easier orientation, the diagram includes thin vertical lines at one-second intervals.
This section comprises a number of labeled bars that run from left to right. Each bar represents a single process during the boot phase. Although some of the bars terminate after a couple of seconds, others drag through to the end: These processes keep running after the boot phase terminates and include services such as the CUPS or the ACPI daemon. To determine when a process starts and when it ends, see where the horizontal bars intersect the vertical timelines. Child processes are connected to the parent processes in the graphic by dotted lines.
Buy Linux Magazine
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters
Support Our Work
Linux Magazine content is made possible with support from readers like you. Please consider contributing when you've found an article to be beneficial.
News
-
The GNU Project Celebrates Its 40th Birthday
September 27 marks the 40th anniversary of the GNU Project, and it was celebrated with a hacker meeting in Biel/Bienne, Switzerland.
-
Linux Kernel Reducing Long-Term Support
LTS support for the Linux kernel is about to undergo some serious changes that will have a considerable impact on the future.
-
Fedora 39 Beta Now Available for Testing
For fans and users of Fedora Linux, the first beta of release 39 is now available, which is a minor upgrade but does include GNOME 45.
-
Fedora Linux 40 to Drop X11 for KDE Plasma
When Fedora 40 arrives in 2024, there will be a few big changes coming, especially for the KDE Plasma option.
-
Real-Time Ubuntu Available in AWS Marketplace
Anyone looking for a Linux distribution for real-time processing could do a whole lot worse than Real-Time Ubuntu.
-
KSMBD Finally Reaches a Stable State
For those who've been looking forward to the first release of KSMBD, after two years it's no longer considered experimental.
-
Nitrux 3.0.0 Has Been Released
The latest version of Nitrux brings plenty of innovation and fresh apps to the table.
-
Linux From Scratch 12.0 Now Available
If you're looking to roll your own Linux distribution, the latest version of Linux From Scratch is now available with plenty of updates.
-
Linux Kernel 6.5 Has Been Released
The newest Linux kernel, version 6.5, now includes initial support for two very exciting features.
-
UbuntuDDE 23.04 Now Available
A new version of the UbuntuDDE remix has finally arrived with all the updates from the Deepin desktop and everything that comes with the Ubuntu 23.04 base.