Making a dynamically-linked root

[Alexey Dokuchaev]

On Tue, Jun 03, 2003 at 09:14:52AM -0700, Matthew Dillon wrote:
> 
> :On Mon, Jun 02, 2003 at 02:25:43PM -0700, Matthew Dillon wrote:
> :>    start!).  Running certain daemon startups in the background might yield
> :>    a significant overall improvement in startup times.  
> :>
> :>    e.g. instead of running 'sshd' you would run sshd in a subshell, aka
> :>    (sshd &), so the RC script can continue on with the next thing without
> :>    having to wait for sshd to fault-in from disk.  Same goes for sendmail
> :>    and many other daemons.
> :
> :This isn't a definite win.  I know in the past it used to actually
> :slow things down: To take your example, having both sshd and sendmail
> :attempting to fault-in from disk in parallel will thrash both the disk
> :and cache far more than sshd and sendmail sequentially faulting in.  A
> :very large number of daemons trying to start in parallel will also
> :stress the scheduler.
> :
> :Peter
> 
>     I'm fairly sure there isn't an issue.  Both a hard drive's own 
>     on-board cache and FreeBSD's clustering and caching code are *very* well
>     suited to this sort of parallel initiation.  There is certainly no
>     scheduler issue.  The key advantage here is that you are removing
>     serialization that would otherwise cause both cpu cycles and disk 
>     cycles to be wasted waiting for each other.  Take sendmail for example.
>     sendmail usually takes upwards of a second to startup due to initial
>     DNS lookups that it makes and other things.  sshd doesn't start 
>     instantaniously either, I think due to creating the initial
>     session keys.

Methinks that Matt's suggestion of (sshd &) and alikes does indeed
sound very cool, and at least worth of reference implementation and
seeing it in action.  As already mentioned by Matt, the bottleneck here
is not in I/O (which is, in fact, really fast nowadays) but in either
network access (in case of sendmail) or (and?) CPU-intensive routines
(speaking of sshd, respectively).

Just my $.02 though, as it all had been already said more or less the
same way by other folks.

./danfe