Tuesday, 17 June 2008

Boot times revisited

I've been fiddling with boot time optimisations for a while now, but it's now born fruit.

If you look at GitHub sidebar on the left right you'll see "my-module-init-tools". I've just published all my baseline fixes.

Coming soon: the module index (already implemented and tested) that speeds up stock Ubuntu boot times by 3 whole seconds! This is on my EEE, remember - a 630Mhz Celeron. But even my Core 2 Duo desktop takes a whole second faffing around reading these module configuration files!

The current maintainer Jon Masters is very interested, but apparently quite busy at the moment.

Next up: UDEV. I had one simple fix to speed rule execution (compute jump targets at load time, instead of scanning at run-time), but the main problem appears to be that it just forks too many processes. I spent ages squeezing the last drops out of string manipulation code etc, because the fork overhead isn't really clear on oprofile. I still don't have a good way to profile it. My planned fix is to move away from directly access to environment variables, use pthreads instead of multiple processes, and then only fork & set environment variables when udev needs to run a different program like modprobe or vol_id.

Altogether, we can expect a modest boot-time improvement for everyone. (Ignoring the few freaks who manage to run a functional system without udev).

Sorry, no convenient links - I've run out of time and need to sleep. You know where the search engine is. (No, it is so not extra effort. Use a proper GUI & browser with support for middle mouse button "paste URL", and default search, aka search from the address bar. Select a word or phrase on the page, middle click, and magic happens. I'm on Konqueror on X11).

No comments: