linux-kernel - Re: [RFC PATCH 0/6] module, kbuild: Faster boot with custom kernel.

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Date:	Mon, 2 Mar 2009 10:27:03 -0800
From:	Arjan van de Ven <arjan@...radead.org>
To:	Kay Sievers <kay.sievers@...y.org>
Cc:	Andreas Robinson <andr345@...il.com>,
	Rusty Russell <rusty@...tcorp.com.au>, sam@...nborg.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 0/6] module, kbuild: Faster boot with custom kernel.

On Mon, 2 Mar 2009 17:29:57 +0100
Kay Sievers <kay.sievers@...y.org> wrote:

> On Mon, Mar 2, 2009 at 17:20, Arjan van de Ven <arjan@...radead.org>
> wrote:
> >> A monolithic kernel with parallelized initcalls is better - about
> >> 200 ms faster than parallel insmods on my test system. However, it
> >> comes with a fairly large set of changes:
> >>
> >> * First, you need a 200-line patch in init/main.c (do_initcalls()
> >> and friends)
> >
> > why?
> > We already have async function calls; and those speed up my boot
> > (when enabled) significantly, by doing much of the kernel/driver
> > init in parallel.
> >
> > My server box boots the whole kernel (including all drivers; I build
> > verything in) in 0.56 seconds, and my net books do it in around 1.0
> > seconds.
> >
> >>
> >> * Then the built-in module dependencies must be calculated
> >> properly, eg with a modified depmod, and added to the build
> >> process.
> >
> > nope not if done right
> >
> >> So, what do you think, should I keep going? IMHO, the slower
> >> userspace implementation is acceptable since it's so much simpler.
> >
> > I would strongly suggest that you turn on the async function calls
> > and look at the boot graph of the resulting kernel boot... if you
> > send that to me I can also take a look and make suggestions....
> 
> The "fastboot" kernel commandline option was used, as mentioned in the
> mail. Is there anything else?

there is some sata level enabling needed depending on the system;
I'd love to see the bootgraph (scripts/bootgraph.pl) for the boot;
that shows exactly what happens when and for how long.

-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org
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