linux-kernel - Re: kms in defconfig

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Date:	Tue, 28 Apr 2009 17:23:11 -0400 (EDT)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Ingo Molnar <mingo@...e.hu>
cc:	Linus Torvalds <torvalds@...ux-foundation.org>, david@...g.hm,
	Tejun Heo <tj@...nel.org>, Dave Airlie <airlied@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: kms in defconfig


On Tue, 28 Apr 2009, Ingo Molnar wrote:
> > 
> > My script requires that you have booted the kernel (or similar 
> > kernel with the same config options and modules). It then runs 
> > lsmod, and searches for the options that enable those modules. It 
> > then reads the current .config file and prints out a new config 
> > that disables all module configs that are not used to enable the 
> > modules found with lsmod.
> > 
> > Here's the code (perl script):
> > 
> > http://rostedt.homelinux.com/code/streamline_config.pl
> > 
> > The instructions on how to use it are at the top of the file.
> > 
> > This script has brought down my full kernel compile times with 
> > distcc from 50 minutes to under 10.
> 
> Looks rather useful IMHO.

There's one little bug. It does not catch configs that are modules that 
depend on other configs as modules (but do not have modules mapped).

I can fix this by also scanning the Kconfig* files, and include any 
"depends on" as well.

> 
> I use the following magic incantation in cfs-debug-info.sh to get to 
> the distro config automatically:
> 
>  KREL=`uname -r | sed 's/smp$//g'`
>  ( cat "`rpm -ql kernel-$KREL 2>/dev/null | grep /boot/config`"
>    cat "`rpm -ql kernel-smp-$KREL 2>/dev/null | grep /boot/config`"
>    cat "`dpkg -L linux-image-$KREL 2>/dev/null | grep /boot/config`"
>    cat /boot/config-$KREL 2>/dev/null
>  )
> 
> Works on most .rpm and .deb based distros. (If /proc/config.gz is 
> present that could be added too.)
> 
> So if this was added as a 'make builtinconfig' kind of shortcut, 
> with no extra steps needed (and if the script bailed out if it 
> cannot find the currently booted .config) - that would be a rather 
> useful (and easy) way to start kernel development on a new box.
> 
> Useful to newbies and oldbies alike IMHO.

Yes, it would be nice to automate this.

-- Steve

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