Network Stack

The Linux kernel initializes the network stack very early, which also costs a little time. If you do not need IPv6, for example, disable the module by editing the /etc/default/grub file again and adding the ipv6.disable=1 option to the GRUB_CMDLINE_LINUX_DEFAULT line. After a reboot, the system only enables the IPv4 stack, which is often all you need on local networks.

Conclusions

The methods described in this article are useful for analyzing the boot process for a Debian installation. Including all the optimizations mentioned in the article, the home-built Linux kernel with integrated i915 driver starts the i8042 driver responsible for the laptop keyboard and touchpad before reaching the 300ms mark (Figure 4). The drivers for ACPI and the Intel graphics card now take the most time, although you could start the Intel driver asynchronously on some systems. Without the initcall_debug parameter, acpi_init takes a few milliseconds less. In all your optimization attempts, you should never forget that measuring can actually influence the measured values.

Figure 4: Following all the optimizations, loading the most important drivers now takes less than 300ms. The drivers for ACPI and the Intel graphics have the largest time share now.

Modern, powerful systems start faster than their predecessors, but they are still too slow considering the potential for savings. One reason for the sluggishness is that installations need to be as universal as possible and work on as many different systems as possible. However, as a normal user, you will not typically need all the features provided with a default system. If you want to take the time and effort, you can tailor the boot process for your own hardware. On a powerful modern system, you might be able to shave off a couple seconds, which could still make a difference to the user experience, but on an older computer with a longer boot time, these techniques could lead to far more significant reductions.