[Cooker] Parallel init for Mandriva

[Couriousous]

Hello

Since a long time I've been thinking about a parallel init implementation in 
Mandriva. Now exam are finished, I've written it.

But there are three major concern about a possible parallel init integration 
in Mandriva, so it was my goal :

	- LSB compliance
	- Does not mix up startup script output
	- Doesn't need heavy modification to current startup script

Let's explain a bit how to make it working :
Every init script can Require and Provide a service. The service name is 
automatically provided. To be parallel-enabled, it _MUST_ contain the 
following line :
# X-Parallel-init
Then, with a such line, the boot processes only take care of requires to know 
when to start the script, there is no more SXXservice ordering.
Requires must be tagged exactly as below on only _one_ line:
# Requires: service1 service2 service3
And provides:
# Provides: provide1 provide2 

If a service requires nothing, you can only set "# X-Parallel-init". If the 
service must be started as the lastest service "# Requires: *" but NO service 
must depend on it. 

Let's come about LSB compliance. If a service doesn't contain the magic "# 
X-Parallel-init" line, it will automatically requires every service who are 
before ( in term of filename ) him, and every service after him will requires 
it. So, it will be started in the same order as in a standard init scheme and 
not in parallel.

How does it keep a clean output ? The output of every service is temporary 
stocked in a file and then when the service startup is over, it's printed on 
the console. The console is accessed by a mutex, so the output is not mixed.

It has a basic requires loop detection and resolution: if service A requires B 
which requires C which requires A. The boot process will deadlock. To avoid 
that, it will broke a requires ( and complain loudly ).

What's missing [ hint: patch welcome ]:
	- Integration with bootsplash, i've started the implementation but I don't 
know how bootsplash works internally.

What are current limitations ( patch also welcome ):
	- If a service requies is provided by two or more service, only the first 
found is effectivly required.
	- Doesn't do exactly what rc script do. If it matter, I can adapt, but I 
don't think it worth the effort.
	- very strict about script syntax
	- isn't bullet proof agains user misuse
	- A lot of other things I haven't thinked at.

What about performance ? see:
http://www.zarb.org/~couriousous/boot/bootchart-normal.png
http://www.zarb.org/~couriousous/boot/bootchart-parallel.png

There is 12 sec gain in boot. It mean a 20% speedup over total boot time and 
~25% speedup over runlevel bootime. We can see now that there are no more 
wait in boot process and the limiting factor is the harddisk.

To try yourself
WARNING! THIS IS PRE-ALPHA SOFTWARE. If you don't know how to repair a system 
with broken initscript, DON'T TRY !!

Download http://www.zarb.org/~couriousous/boot/prcsys.c 
compile it with gcc -Wall prcsys.c -lpthread -o prcsys
then put the "prcsys" binary in /sbin

Download http://www.zarb.org/~couriousous/boot/rc.patch then apply it 
to /etc/rc.d/rc file. 

Then goto http://www.zarb.org/~couriousous/boot/services/ and pick the patch 
for each service you want to convert. There are not a patch for every service 
in the distribution, I will produce more if there are interest to do it. 
Alternatively you can do it yourself with the above explanations and 
contribute it back.

Then reboot and put "pinit" as kernel parameter. If you don't do it, it will 
fall back to the classical boot.

Regards,
Couriousous