Faster login

[David Zeuthen]

Hi,

So I had a brief look at shortening startup/login time and tried
disabling rhgb in favor of starting gdm early. It looks pretty
promising; here are some wall-clock numbers from two runs of each
configuration:

                       |   gdm_early  |   rhgb+gdm   |
 ----------------------+------+-------+-------+------+
 GRUB timeout          | 0:00 | 0:00  |  0:00 | 0:00 |
 Starting udev         | 0:13 | 0:13  |  0:13 | 0:14 |
 HW init done          | 0:25 | 0:25  |  0:26 | 0:26 |
 rhgb visible          |  N/A |  N/A  |  0:36 | 0:35 |
 gdm login visible     | 0:43 | 0:44  |  1:25 | 1:26 |
 gdm login entered     | 0:52 | 0:52  |  1:31 | 1:32 |
 GNOME banner visible  | 1:13 | 1:14  |  1:40 | 1:41 |
 Nautilus Background   | 1:33 | 1:32  |  1:51 | 1:52 |
 Panel visible         | 1:43 | 1:43  |  2:02 | 2:02 |
 HD activity off       | 1:59 | 1:56  |  2:13 | 2:14 |

The milestones should be pretty self evident. This is on a stock FC3
system running on a IBM T41 1.6GHz (running on AC power), 512MB RAM
without any services manually disabled. 

In addition to starting gdm early, the modifications also start up a few
services, D-BUS, HAL and NetworkManager, that is critical to the GNOME
desktop.

Some random thoughts/observations:

 - We get the gdm window 40 secs faster 

 - The 12 secs from "Starting udev" to "HW init done" can be mostly
   shaved away/run in parallel

 - Kernel bootstrap time (13 secs) can probably be much shorter
   (that's what some kernel guys say anyway)

 - With this hack we shave twenty secs of the booting time (e.g. from
   GRUB until you can use your PC) but booting still feels much quicker
   because of the interaction with gdm in the middle (YMMV; e.g. placebo
   effect etc.)

 - rhgb+gdm spawns an X server each which is sort of stupid and unsafe
   (or so some Xorg guys tell me). This solution, per design, avoids
   doing that

 - we don't get the kudzu screen nor the fsck screens or any other
   console interactions. However, IMHO, such screens are not good UI
   in the first place - we should instead have GUI replacemnts that
   possibly notifies you when you log into the desktop session (stuff
   like NetworkManager and HAL alleviates such problems for networking
   and storage devices)

 - we don't get service startup notification, but, uhmm, is it really
   useful learning that the "Console Mouse Service" or "Printing Sub-
   system" have started? Instead, this stuff could just be put in gdm

 - it could be interesting to make /sbin/init own a D-BUS service that
   gdm and other stuff can query and interact with. Could also be fun
   to completely replace it with something a'la the SystemServices
   prototype that Seth did last year; links

   http://www.osnews.com/story.php?news_id=4711
   http://www.gnome.org/~seth/blog/2003/Sep/27

 - Could be interesting to instrument the kernel with some pagefault
   counters etc. and attempt do more readahead on e.g. the GNOME libs
   (both Windows XP and Mac OS X does all that; I think we do too but
   I've been told it can be improved)

So, anyway, I think it could be interesting to discuss starting gdm
instead of rhgb. If you want to try out my crude hack, grab the file
here

 http://people.redhat.com/davidz/newinit.sh

put it in on your system as /newinit.sh, chmod a+x it and change this
line /etc/inittab

 si::sysinit:/etc/rc.d/rc.sysinit

to these two lines

 #si::sysinit:/etc/rc.d/rc.sysinit
 si::sysinit:/newinit.sh

and you should be set to go! If it breaks you get to keep both pieces;
e.g. try this at your own risk [1].

Cheers,
David

[1] :if it doesn't work you can boot your kernel with init=/bin/sh, do a
'mount -n -o remount,rw /' and edit your /etc/inittab file to point to
the original sysinit.