booting optimization

[Constantinos Maltezos]

On Friday 22 August 2008 1:39:59 am O. Sinclair wrote:
> Pastor JW wrote:
> > I came across this while looking through /etc/init.d/rc to see what
> > things do. There is a line which is "CONCURRENCY=none" there so I changed
> > the "none" to "shell" like the comment indicates is a viable option and
> > booting became MUCH faster!  I wouldn't mind finding more things like
> > this but my 1525n laptop is now lightning fast upon booting!  ;)
>
> I have the same experience! Anyone have an idea what this setting
> "actually" does/means?
>
> Sinclair

If you've ever watched the console messages during boot, you will see messages 
telling you that certain things are starting and the like.  Traditionally, all 
the modules and services and whatnot that get loaded at this time go one after 
the other, taking turns as it were.  When you enable concurrency, it loads as 
many of them as it can at once and in that way, the processes run 
concurrently.  This is why it's faster.  The old way is strictly dependent on 
processor speed, the concurrent way is dependent on processor speed *and* 
memory and will almost always be faster.  The only problem I can imagine 
realistically is if fsck is chosen to run at boot at any point.  But there may 
be code in the hack that tells everything else to wait until fsck finishes.