Avoiding autoloading

On a faster computer, autoloading might not be a big deal. But on this 300Mhz Pentium II, it causes a considerable boot delay.

The problem, as I understand it, is that the autoloading sequence first senses the modules you need, then loads them in the correct order.

Which is fine, except on a machine like this — a laptop, with no real opportunities for hardware changes — it’s really only needed once. After that, if I run into a hardware switch, autosensing the modules it needs would probably be nice. But that’s one boot out of a thousand, and I’m just weird enough to convince myself that I need a rebuild if I get a new piece of hardware. I’m a glutton for punishment. … 🙄

Disabling autoloading does cause one problem, though: Modules have to be inserted in the proper order for some of them to work. It’s just like dependencies. If you try to start something and it’s missing another piece, it’s going to crap out on you. Only this time you’ll be left without a mouse. Or video. Or a functioning hard drive.

I installed hwdetect via pacman, and started it with the –show-modules flag. This is the output, on my nifty Dell Latitude CPi A300XT:

AGP : agpgart intel-agp
PATA : ata_generic
SATA : ata_piix
USB : usbcore uhci-hcd
NET : ppp_generic slhc ieee80211_crypt hermes hostap hostap_cs orinoco orinoco_cs
INPUT : evdev pcspkr psmouse serio_raw tsdev
PCMCIA : pcmcia pcmcia_core rsrc_nonstatic yenta_socket
SOUND : snd-mixer-oss snd-pcm-oss snd-page-alloc snd-pcm snd-timer snd snd-ac97-bus snd-ac97-codec snd-nm256 soundcore
OTHER : cdrom lp ppdev rtc i2c-piix4 i2c-core parport parport_pc pci_hotplug shpchp

Unless I’m mistaken, those are all the modules this system needs to function properly.

I’ve seen another way of doing this since I tried it, a couple of days ago. This is modified slightly from a seemingly unrelated post on the Arch forums:

modprobe -a --show-depends $(find /sys/devices/ -name modalias -exec cat {} + ) | sort -u

I think the net effect is the same, although the second method does leave in the paths to the modules. For my purposes, the first method was preferable. I copied that into a text file and made it into a raw list of modules.

Then I did a little Googling and tried to figure out what each module did, and whether or not I wanted to keep it. Some were easy; I don’t use a modem, so I suspected ppp_generic of being useless to me. It was, and was thrown out as a result. Same with parport and parport_pc, and some others.

To test it, I blacklisted the module in rc.conf but kept autoloading enabled, and rebooted. If things worked, it was discarded. If not … well, as an example, I thought serio_raw would be pointless, but when I blacklisted it and rebooted with autoloading still enabled, I suddenly had no external mouse. So you can’t be sure. Keep autoloading on for a while and blacklist to test.

(It’s worth mentioning at this point that there’s a load_modules=off flag that might save you if you’re having problems booting after tweaking your modules. It’s a one-time emergency override that prevents any modules from loading, which means almost nothing will work … but on the other hand, you should be able to get back on your feet.)

After about 20 minutes of searching and Googling, I had two lists: needed and unneeded.

agpgart intel-agp ata_generic ata_piix usbcore uhci-hcd ieee80211_crypt hermes hostap hostap_cs orinoco orinoco_cs evdev pcspkr psmouse serio_raw pcmcia pcmcia_core rsrc_nonstatic yenta_socket snd-mixer-oss snd-pcm-oss snd-page-alloc snd-pcm snd-timer snd snd-ac97-bus snd-ac97-codec snd-nm256 soundcore cdrom rtc i2c-piix4 i2c-core pci_hotplug

shpchp parport parport_pc lp ppdev tsdev ppp_generic slhc

I blacklisted all the unneeded modules, and rebooting worked fine. And yet, if I copy those needed modules into the MODULES=() line, I still ended up with a borked system. That’s the dependencies playing tricks on you again.

I don’t know if there’s a better way to do this, and if there is, I’d love to hear about it. But my solution was to search through the modules.dep file, which has a canonical list of modules available on your system, sorted in insertion order.

Open nano -w /lib/modules/`uname -r`/modules.dep. It’ll probably be about 1450 lines long, if not longer. So be patient on an older system.

Use CTRL+W (the “Where Is” search) to search for the name of the module with a .ko suffix. Make sure you’re on the line that lists that module, then press CTRL+C, which will show you the line count.

Keep a list of all those modules and the lines they appear on. Something like this:

agpgart 943
intel-agp 949
ata_generic 1108
ata_piix 1086
usbcore 1179
uhci-hcd 498
ieee80211_crypt 843
hermes 861
hostap 856
hostap_cs 858
orinoco 861
orinoco_cs 848
evdev 737
psmouse 736
serio_raw 719
pcmcia 839
pcmcia_core 839
rsrc_nonstatic 1002
yenta_socket 1007
snd-mixer-oss 249
snd-pcm-oss 249
snd-page-alloc 249
snd-pcm 264
snd-timer 264
snd 264
snd-ac97-bus 266
snd-ac97-codec 267
snd-nm256 289
soundcore 289
cdrom 663
rtc 980
i2c-piix4 1055
i2c-core 1055
pci_hotplug 682

It’s an ugly list, but when you’ve sorted all those into the order determined by their line numbers, you have a perfect, concise and sorted list of all the modules your machine needs — that you want, that is.

Now go back into the rc.conf file, turn off autoloading and insert those lines into the MODULES=() line. In my case, it looked like this:

MODULES=(snd-mixer-oss snd-pcm-oss snd-page-alloc snd-pcm snd-timer snd snd-ac97-bus snd-ac97-codec snd-nm256 soundcore uhci-hcd cdrom pci_hotplug serio_raw psmouse evdev pcmcia pcmcia_core ieee80211_crypt orinoco_cs hostap hostap_cs hermes orinoco agpgart intel-agp rtc rsrc_nonstatic yenta_socket i2c-piix4 i2c-core ata_piix ata_generic usbcore)

(Don’t ask me why the sound stuff is at the front. I just work here.) You can comment out the MOD_BLACKLIST line now, unless you feel safer with your unneeded modules in there. If autoloading is off and you’ve inserted the modules you want manually, they shouldn’t ever be touched.

On reboot, my machine was working great — external mouse, touchpad, video, audio, even wireless. No problems whatsoever.

If I was better at scripting, perhaps I could come up with a more elegant way of doing this than to output a list, sort it, search-search-search, sort-sort-sort, and then rebuild it into a shape that rc.conf wants.

But for now, I’m content: My boot time went from 46.13 seconds to 42.24! 😀