This patch allows you to background a whole sequence of daemons, rather than an individual daemon. As a result, you can get a very fast parallel boot. I suppose this could be considered an 'arch like' parallel boot setup. This isn't my idea, I'm sure someone has made a patch like this before however I couldnt find it and it never got merged.
The major benefit is that boot doesnt get held up by slow starting dependencies, like hal and network. I can't background network because I have other services that depend on it such as nfs, ssh, iptables, ntpdate and cups. Similarly, I cant background hal, as gdm depends on it.
ssh, iptables and cups can be started before your network is up... even more, iptables SHOULD be started before network is up, since it needs to protect you from the first moment
For example... DAEMONS=(@net-auto,ntpdate,cups @acpi,hal,gdm syslog-ng cpufreq bluetooth crond) Comma delimited groups are started in background and run in sequence.
Bootchart testing I saw a consistent improvement of at least 5s, from 31s to 26s. One boot somehow acheived 23s, and that was with full auto wireless enabled. I used a fixed modules list to avoid any inconsistency in udev time, so udev was always 1.9-2.1 seconds. I also used a wired connection for network as wireless connection time varied too much. There is a more noticable improvement with wireless, as it takes longer and can be backgrounded with the patch.
-- damjan