Boot Performance Targets for Karmic and +1

Martin Pitt martin.pitt at
Tue Jun 9 09:40:24 BST 2009

Hello Scott,

thanks for this excellent summary!

Scott James Remnant [2009-06-08 16:07 +0100]:
> The dependencies of the X server are:
> [...]
> In otherwords, "udev".  udev has no real dependencies other than being
> out of the initramfs.
> This means that the only thing holding us up loading X is udev, and the
> initramfs.  Some encouraging work has been done to udev which I hope to
> talk about in a future mail, so really the problem is the initramfs.
> [...]
>   2s  Kernel and initramfs.
>       This includes both, since arguably the need for an initramfs is a
>       kernel implementation detail anyway (the kernel can mount the root
>       filesystem itself in many circumstances)

I think there's one important piece missing here: readahead. Right now
we do that in a single big chunk, right after initramfs. On my box it
takes about 7 seconds; I guess it's faster on your's, but it would
still not even closely fit into the 2s + 2s second budget.

Can we sensibly split readahead to read the X bits first, and then
everything else in a second block? This might not be relevant with
sreadahead and SSDs (since stuff gets read in usage order), but is a
problem on rotary disks (where readahead reads them in disk block



Martin Pitt                        |
Ubuntu Developer (  | Debian Developer  (
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