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From: Rusty Russell <rusty@rustcorp.com.au>
To: Andreas Robinson <andr345@gmail.com>
Subject: Re: [RFC PATCH 0/6] module, kbuild: Faster boot with custom kernel.
Date: Tue, 24 Feb 2009 11:57:10 +1030
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Cc: Kay Sievers <kay.sievers@vrfy.org>, sam@ravnborg.org,
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On Friday 20 February 2009 11:07:05 Andreas Robinson wrote:
> 1. Monolithic:  6.27 s, (0.22). bzImg=3419 kB ramfs=515 kB
> 2. Megamodule:  6.80 s, (0.16). bzImg=2297 kB ramfs=1783 kB
> 3. Insmod list: 6.83 s, (0.07). bzImg=2297 kB ramfs=1942 kB
> 
> 10 samples were taken in each case. Standard deviations are in parenthesis.
> The measured times are printk timestamps from a dummy module inserted last.
> 
> Reading these benchmark results I can only conclude that my work is
> useless and life has no meaning.

I know that feeling!  Performance work tends to be like that.  I assume this
is an unpatched kernel, or did you apply some of the stop_machine prevention
/ lock reduction patches?
 
> So, what's missing or been done wrong here? I expected the difference
> between monolithic and modular to be greater to be honest.

modprobe vs insmod?

You could try copying /lib/modules/`uname -r`/modules.* and using modprobe,
see if the slowdown is actually there.

Thanks for chasing this!
Rusty.
Rusty.