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

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Message-ID: <ac3eb2510902170353ia62a630nbe5cf059ca7d616e@mail.gmail.com>
Date:	Tue, 17 Feb 2009 12:53:25 +0100
From:	Kay Sievers <kay.sievers@...y.org>
To:	Andreas Robinson <andr345@...il.com>
Cc:	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 Tue, Feb 17, 2009 at 11:42, Andreas Robinson <andr345@...il.com> wrote:
> On Mon, Feb 16, 2009 at 11:51 PM, Rusty Russell <rusty@...tcorp.com.au> wrote:
>>
>>  This isn't crazy.  But you'd need to benchmark against the minimal
>> userspace solution: a binary with all the modules built into
>> it which calls sys_init_module on each one, then does the root swizzle
>> or whatever.
>>
>> I think you'd find the difference to be in the noise.

Usual distro setups load like 100+ modules on every bootup. Modprobing
and symbol-resolving is serialized and uses stop_machine(), so there
might be some significant difference here when loading a huge number
of modules individually. Monolithic versus modular kernels usually
make about 2+ seconds difference on a recent laptop.

> your're right and I'll get right on it.

For distros it's probably more interesting not to get rid of the
initramfs, but possibly have the mkinitrd/mkinitramfs tool to pre-link
all the usual modules if faster bootup is expected. Having only the
few modules pre-linked which are usually included in the initramfs,
might, as Rusty expects, not make that much difference.

Kay
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