X205TA - Minimal Initramfs

Improving Boot Performance:

Everybody wants their computer to be faster. That includes starting up faster. This is obviously true if you’re hosting a server, but even for personal use. Admitedly, I don’t think it’s that important for a high end desktop rig that you leave on (or suspended) all the time.

However, my current workstation is a modest Asus X205TA.
In fact, I have GitHub repo specifically for tweaking this machine. At any rate, with a portable machine, starting up quickly is paramount.

This post will specifcally cover customizing / creating a minimal Linux kernel.
For more performance options, see the relevant Arch Wiki article on the subject.

My Process:

The Arch Wiki references this tutorial, whcih provides a conceptual understanding of what we’re doing here (creating a kernel with only the modules required to boot your system) but lacks the specifics for this machine (Asus X205TA).

1. Take note of the modules listed in the output of:

   $ lspci -vk | grep "Kernel modules"

2. Next, take note of the output from

   $ udevadm info --attribute-walk -n /dev/mmcblk0 | grep 'DRIVERS'

3. Then check over the output of $ lsmod with the modules the above command found. You’ll need to include any dependencies as well. (e.g. sdhci_acpi > sdhci > mmc_block > mmc_core)

4. Next, take note of what your root filesystem is as mentioned in the referenced tutorial. Likely, the module name is just the name of the filesystem, with a few exceptions.

5. Then I created an alternate mkinitcpio.conf. I didin’t want to bork my existing config during the testing stages. (If you do not want to use th eminimal config for kernel updates, you’ll need to follow this step as well )

    # cp /etc/mkinitcpio.conf /etc/mkinitcpio-tiny.conf 
    # nano /etc/mkinitcpio-tiny.conf
   

   • Cut down the HOOKS array to only include “base.”
   • In the “BINARIES” array, include “fsck” and “fsck.your_filesystem.”
   • The “MODULES” array should contain the long list of modules you’ve been collecting in the steps above.

6. I’ll save everyone the trail and error I had to go through to find out which ones were essential. Below is the most minimal I could make.

    /etc/mkinitcpio-tiny.conf
    -----
    MODULES="your_filesystem mmc_block sdhci sdhci_acpi i915"        
    BINARIES="fsck fsck.f2fs"   
    HOOKS="base"
   

7. After that, create the kernel image via:

   # mkinitcpio -c /etc/mkinitcpio-tiny.conf -g /boot/initramfs-linux-tiny.img

8. Finally, add an entry to your boot loarder which selects the custom image. In my case (systemd-boot) that means:

    /boot/loader/entries/tiny.conf
    -----
    title Arch Linux i686 - Tiny
    linux /vmlinuz-linux
    initrd /initramfs-linux-tiny.img
   

Results:

There’s nothing mindblowing here. I certainly wouldn’t complain too much about the single digit boot time I achieved before this process, but it was worth an afternoon of tinkering.

Image Size:

Before

$ du -sh /boot/initramfs-linux.img
-----
3.1M    /boot/initramfs-linux.img

After

$ du -sh /boot/initramfs-linux-tiny.img
-----
2.9M    /boot/initramfs-linux-tiny.img

Boot Time:

Before (mount options: rw intel_idle.max_cstate=1)

$ systemd-analyze
-----
Startup finished in 4.425s (firmware) + 174ms (loader) + 
1.363 (kernel) + 2.876s (userspace) = 9.630s

After (mount options: rw intel_idle.max_cstate=1 discard relatime noacl background_gc=on inline_data active_logs=6)

$ systemd-analyze
-----
Startup finished in 3.423s (frimware) + 166ms (loader) + 
2.71s (kernel) + 1.558s (userspace) = 7.864s

PS: Other Boot Performance Tips Include: removing daemons that start on boot, tuning your filesystem’s mount options, set your bootloader’s timeout delay to 0 seconds.