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

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Message-ID: <ac3eb2510902180115o4690a335n129e4df695540de0@mail.gmail.com>
Date:	Wed, 18 Feb 2009 10:15:21 +0100
From:	Kay Sievers <kay.sievers@...y.org>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	Andreas Robinson <andr345@...il.com>, sam@...nborg.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 0/6] module, kbuild: Faster boot with custom kernel.

On Wed, Feb 18, 2009 at 05:58, Rusty Russell <rusty@...tcorp.com.au> wrote:
> On Tuesday 17 February 2009 22:23:25 Kay Sievers wrote:
>> Monolithic versus modular kernels usually
>> make about 2+ seconds difference on a recent laptop.
>
> Thanks for the fact injection.  How about a megamodule then?

Sounds interesting. The ability to load multiple modules with a single
call may help, if such a call could be handled faster than individual
calls. Modprobe's modules added by dependencies of the requested
module, or modprobe -a could probably use such a facility.

Or do you think, the time the kernel needs to be locked can be
minimized somehow, so we get more parallelism and less serialization?

The current load_module() wraps ~400 lines of pretty heavy code in
stop_machine(), if we could possibly make that window smaller, so that
multiple instances could prepare some of the work in parallel, and
only a fraction of the current work would need to be serialized?

If that could be improved for the common distro case of running ~90
modprobe calls on bootup, many of them running in parallel, linking
~100 modules in, all in a time-frame of ~2-3 seconds -- that maybe
would attack the real "problem"?

Thanks,
Kay
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