Speeding up live cd boot through optimizing file layout

Matt Zimmerman mdz at ubuntu.com
Thu Jun 8 10:33:32 BST 2006

On Thu, Jun 08, 2006 at 11:20:09AM +0200, Krzysztof Lichota wrote:
> Matt Zimmerman napisał(a):
> > Don't assume that it's perfect; hard disks are much more forgiving in this
> > respect than CDs.
> I don't understand. What hard disk? I meant the list created by my
> tracing facility in SquashFS and list of readahead files as present in
> ISO image.

The lists in /etc/readahead are only updated when someone manually uses the
profiling mechanism, so they get out of date sometimes.  This is not
necessarily noticeable on a disk-based system, but would be on a CD.

> > I think block-level readahead might work better, since probably only a
> > relatively small portion of each file is accessed during startup.
> This can be done as SquashFS can print block numbers or my tracing
> facility can be extended to print offset in file.
> Unfortunately block-level layout cannot be done as SquashFS uses
> continuous file allocation :)

I think squashfs will defeat our efforts here somewhat due to the blocksize
it uses for compression, but only an experiment will say for sure.

 - mdz

More information about the ubuntu-devel mailing list