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Petter Reinholdtsen 05-06-2010 07:11 PM

Parallellizing the boot in Debian Squeeze - ready for wider testing
 
These days, the init.d script dependencies in Squeeze are quite
complete, so complete that it is actually possible to run all the
init.d scripts in parallell based on these dependencies. If you want
to test your Squeeze system, make sure dependency based boot
sequencing is enabled, and add this line to /etc/default/rcS:

CONCURRENCY=makefile

That is it. It will cause sysv-rc to use the startpar tool to run
scripts in parallel using the dependency information stored in
/etc/init.d/.depend.boot, /etc/init.d/.depend.start and
/etc/init.d/.depend.stop to order the scripts. Startpar is configured
to try to start the kdm and gdm scripts as early as possible, and will
start the facilities required by kdm or gdm as early as possible to
make this happen.

Give it a try, and see if you like the result. If some services fail
to start properly, it is most likely because they have incomplete
init.d script dependencies in their startup script (or some of their
dependent scripts have incomplete dependencies). Report bugs and get
the package maintainers to fix it. :)

Running scripts in parallel could be the default in Debian when we
manage to get the init.d script dependencies complete and correct. I
expect we will get there in Squeeze+1, if we get manage to test and
fix the remaining issues.

If you report any problems with dependencies in init.d scripts to the
BTS, please usertag the report to get it to show up at
<URL: http://bugs.debian.org/cgi-bin/pkgreport.cgi?users=initscripts-ng-devel@lists.alioth.debian.org >.

Happy hacking,
--
Petter Reinholdtsen


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Stefano Zacchiroli 05-07-2010 07:26 AM

Parallellizing the boot in Debian Squeeze - ready for wider testing
 
On Thu, May 06, 2010 at 09:11:56PM +0200, Petter Reinholdtsen wrote:
> These days, the init.d script dependencies in Squeeze are quite
> complete, so complete that it is actually possible to run all the
> init.d scripts in parallell based on these dependencies.
<snip>
> Running scripts in parallel could be the default in Debian when we
> manage to get the init.d script dependencies complete and correct. I
> expect we will get there in Squeeze+1, if we get manage to test and
> fix the remaining issues.

From your message I can't exactly tell why we can't have it for
Squeeze. My personal experience is that I've been using
CONCURRENCY=makefile since several months now, and I've never run into
problems.

Can't we just make it the default for Squeeze? (which would presumably
mean changing the default *now* in testing to seek the most feedback
possible before the actual release) If not, do you have a list of bugs
that block us from doing that? Or comments from the release team that
consider that not appropriate, or ...

The init.d world has changed quite a bit in recent years and might
change even more in the next, it is possible that for Squeeze+1 we'll
want to be elsewhere than at CONCURRENCY=makefile.

Cheers.

--
Stefano Zacchiroli -o- PhD in Computer Science PostDoc @ Univ. Paris 7
zack@{upsilon.cc,pps.jussieu.fr,debian.org} -<>- http://upsilon.cc/zack/
Dietro un grande uomo c' ..| . |. Et ne m'en veux pas si je te tutoie
sempre uno zaino ...........| ..: |.... Je dis tu tous ceux que j'aime

Mike Hommey 05-07-2010 07:59 AM

Parallellizing the boot in Debian Squeeze - ready for wider testing
 
On Fri, May 07, 2010 at 09:47:36AM +0200, Josselin Mouette wrote:
> Le jeudi 06 mai 2010 * 21:11 +0200, Petter Reinholdtsen a écrit :
> > These days, the init.d script dependencies in Squeeze are quite
> > complete, so complete that it is actually possible to run all the
> > init.d scripts in parallell based on these dependencies. If you want
> > to test your Squeeze system, make sure dependency based boot
> > sequencing is enabled, and add this line to /etc/default/rcS:
> >
> > CONCURRENCY=makefile
>
> Seems to work fine for me. However the gain isn’t really important,
> given that the critical path includes fsck and networking.

And kernel+initramfs. That's more than half the boot time (without
even CONCURRENCY=makefile) here.

Mike


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Petter Reinholdtsen 05-07-2010 08:06 AM

Parallellizing the boot in Debian Squeeze - ready for wider testing
 
[Stefano Zacchiroli]
> From your message I can't exactly tell why we can't have it for
> Squeeze. My personal experience is that I've been using
> CONCURRENCY=makefile since several months now, and I've never run
> into problems.

I know there are bugs in the dependencies, which only affect some
combinations of packages when concurrent booting is enabled (example:
#508289) , and believe the number of users testing with
CONCURRENCY=makefile is so low that it is unlikely that all such bugs
have been found and detected. There is also the issue with booting
too fast exposing race conditions, where the boot just happen to work
now in sequential mode. I ran into issues with X failing to start
when CONCURRENCY=makefile and readahead were both enabled, and never
found time to track down the problem. I suspect the cause is that
some services are not operational when their init.d script is
finished, causing their depending scripts to fail if the boot happen
too quickly.

And I also got the idea that Squeeze will freeze fairly soon, and
given my believe that there are edge cases and race conditions left to
fix, introducing it shortly before freeze seem like a bad idea.

All of this is based on my belief that there are very few people
testing with CONCURRENCY=makefile. If a lot of people are using it
successfully, it is less likely that there are many race conditions
and edge cases left to fix, and enabling it for Squeeze would be a
more safe option.

Working with the boot system tend to make me very careful when
introducing changes, as a wrong upload can render a lot of machines
unable to boot. :)

> The init.d world has changed quite a bit in recent years and might
> change even more in the next, it is possible that for Squeeze+1
> we'll want to be elsewhere than at CONCURRENCY=makefile.

I am quite sure we will still have init.d scripts around (the LSB
require it), but I also hope we have replaced /sbin/init with an event
based system, pushed most scripts out of rcS.d/ and into rc[2-5].d or
event triggers. It should both solve the broken single user in Debian
and make sure machines boot no matter the type of hardware
connected. :)

Happy hacking,
--
Petter Reinholdtsen


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Goswin von Brederlow 05-07-2010 08:22 AM

Parallellizing the boot in Debian Squeeze - ready for wider testing
 
Stefano Zacchiroli <zack@debian.org> writes:

> On Thu, May 06, 2010 at 09:11:56PM +0200, Petter Reinholdtsen wrote:
>> These days, the init.d script dependencies in Squeeze are quite
>> complete, so complete that it is actually possible to run all the
>> init.d scripts in parallell based on these dependencies.
> <snip>
>> Running scripts in parallel could be the default in Debian when we
>> manage to get the init.d script dependencies complete and correct. I
>> expect we will get there in Squeeze+1, if we get manage to test and
>> fix the remaining issues.
>
> From your message I can't exactly tell why we can't have it for
> Squeeze. My personal experience is that I've been using
> CONCURRENCY=makefile since several months now, and I've never run into
> problems.
>
> Can't we just make it the default for Squeeze? (which would presumably
> mean changing the default *now* in testing to seek the most feedback
> possible before the actual release) If not, do you have a list of bugs
> that block us from doing that? Or comments from the release team that
> consider that not appropriate, or ...

Did you actualy read the mail till the end?

http://bugs.debian.org/cgi-bin/pkgreport.cgi?users=initscripts-ng-devel@lists.alioth.debian.org

> The init.d world has changed quite a bit in recent years and might
> change even more in the next, it is possible that for Squeeze+1 we'll
> want to be elsewhere than at CONCURRENCY=makefile.

Yet again?

> Cheers.

MfG
Goswin


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Stefano Zacchiroli 05-07-2010 09:47 AM

Parallellizing the boot in Debian Squeeze - ready for wider testing
 
On Fri, May 07, 2010 at 10:22:14AM +0200, Goswin von Brederlow wrote:
> Did you actualy read the mail till the end?
> http://bugs.debian.org/cgi-bin/pkgreport.cgi?users=initscripts-ng-devel@lists.alioth.debian.org

Yes, I did, and I noticed that none of those bugs are RC severity,
that's why I've explicitly asked for "blockers" (and yes, I could have
been explicit about that distinction in my mail).

Cheers.

--
Stefano Zacchiroli -o- PhD in Computer Science PostDoc @ Univ. Paris 7
zack@{upsilon.cc,pps.jussieu.fr,debian.org} -<>- http://upsilon.cc/zack/
Dietro un grande uomo c' ..| . |. Et ne m'en veux pas si je te tutoie
sempre uno zaino ...........| ..: |.... Je dis tu tous ceux que j'aime

Aaron Toponce 05-07-2010 12:45 PM

Parallellizing the boot in Debian Squeeze - ready for wider testing
 
On 5/7/2010 2:33 AM, Paul Wise wrote:
> Other distros are using upstart:
>
> http://upstart.ubuntu.com/

I thought Upstart was on the list for release in Sqeeze. Has this changed?

http://lists.debian.org/debian-devel-announce/2009/09/msg00003.html

--
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. . O . O O O . O . O O . . O
O O O . O . . O O O O . O O O

Petter Reinholdtsen 05-07-2010 12:57 PM

Parallellizing the boot in Debian Squeeze - ready for wider testing
 
[Aaron Toponce]
> I thought Upstart was on the list for release in Sqeeze. Has this changed?
>
> http://lists.debian.org/debian-devel-announce/2009/09/msg00003.html

It is still on the wishlist, but the needed pieces are not ready, so
it seem unlikely to happen this late in the release process. At the
moment, I believe it will happen shortly after Squeeze is released, if
the needed pieces are ready by then.

Happy hacking,
--
Petter Reinholdtsen


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Julien Cristau 05-07-2010 01:15 PM

Parallellizing the boot in Debian Squeeze - ready for wider testing
 
On Fri, May 7, 2010 at 14:57:08 +0200, Petter Reinholdtsen wrote:

>
> [Aaron Toponce]
> > I thought Upstart was on the list for release in Sqeeze. Has this changed?
> >
> > http://lists.debian.org/debian-devel-announce/2009/09/msg00003.html
>
> It is still on the wishlist, but the needed pieces are not ready, so
> it seem unlikely to happen this late in the release process. At the
> moment, I believe it will happen shortly after Squeeze is released, if
> the needed pieces are ready by then.
>
What are the "needed pieces"?

Cheers,
Julien

Petter Reinholdtsen 05-07-2010 01:29 PM

Parallellizing the boot in Debian Squeeze - ready for wider testing
 
[Julien Cristau]
> What are the "needed pieces"?

I am sorry, do not have time to write a full update, so I give a quick
pointer instead. The list we use to discuss the boot system work is
initscripts-ng-devel@. See for example
<URL: http://lists.alioth.debian.org/pipermail/initscripts-ng-devel/2010-March/000844.html >
for a peek into the status.

Happy hacking,
--
Petter Reinholdtsten


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