linux-kernel - Re: [PATCH 0/3] removing unwanted module configs

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Message-ID: <20090430071830.GC16737@elte.hu>
Date:	Thu, 30 Apr 2009 09:18:30 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Theodore Tso <tytso@....edu>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	zippel@...ux-m68k.org, linux-kbuild@...r.kernel.org,
	Sam Ravnborg <sam@...nborg.org>,
	Jonathan Corbet <corbet@....net>
Subject: Re: [PATCH 0/3] removing unwanted module configs


* Steven Rostedt <rostedt@...dmis.org> wrote:

> As it has been brought up last Kernel Summit, we want to make it easier
> for those that report bugs to build their own kernels, and maybe even
> bisect with git.  Some of these people are not programmers and do not
> understand the complexity of the configuration options. But to compile
> a distribution configured kernel on their boxes can take hours.
> 
> This patch series comes to the rescue. I wrote the first instance of
> streamline config when I bought a new box in 2005 and got frustrated
> with finding all the necessary configurations to boot it. It is a
> small (yet powerful) perl script.
> 
> Here's what it does:
> 
>  * Reads the modules that are load by using lsmod.
>  * Reads all Makefiles to map modules to CONFIG_* options
>  * Reads the Kconfig files to find dependencies and selects
>  * Figures out what CONFIGS are needed to compile the loaded modules
>  * Reads the .config and prints out a version with all module configurations
>     that not needed, disabled.
> 
> The next two patches add options to make.
> 
>  localmodconfig - this will run streamline_config.pl on the .config file
> 	and replace it at the end.
> 
>  localyesconfig - this will do the same as localmodconfig but will also
> 	sed -i s/=m/=y/  to turn all modules to core. It will also run
> 	the 'make oldcondfig' to fix it up and let the user handle
> 	andything that was changed by converting a module to core.
> 
> Anyway, this is now in git and as a series of patches here. My git 
> tree is based off of the latest Linus git tree.
> 
> Have fun!

Very nice and useful!

I have given it a try - it works to a certain degree, but does not 
seem to work fully. If i boot a Fedora distro kernel with this 
module setup:

aldebaran:~/linux/linux> lsmod
Module                  Size  Used by
sunrpc                253904  1 
ipv6                  349568  50 
cpufreq_ondemand       73248  0 
acpi_cpufreq           75408  0 
freq_table             70400  2 cpufreq_ondemand,acpi_cpufreq
dm_multipath           82256  0 
i2c_i801               75932  0 
i2c_core               87192  1 i2c_i801
serio_raw              71556  0 
pcspkr                 68352  0 
pata_jmicron           69504  0 
iTCO_wdt               78208  0 
shpchp                 99160  0 
iTCO_vendor_support    68868  1 iTCO_wdt
igb                   144412  0 
dca                    71976  1 igb
pata_acpi              70528  0 
ata_generic            71428  0 

note the 'igb' driver that is essential to be picked up. 'make 
localyesconfig' complains:

  module igb did not have configs CONFIG_IGB

But:

  # CONFIG_IGB is not set

It did pick up other essential drivers - such as ext3. Why did it 
miss IGB? Here are all the missed drivers:

aldebaran:~/linux/linux> make localyesconfig
module ata_generic did not have configs CONFIG_ATA_GENERIC
module iTCO_vendor_support did not have configs CONFIG_ITCO_WDT
module shpchp did not have configs CONFIG_HOTPLUG_PCI_SHPC
module acpi_cpufreq did not have configs CONFIG_IA64_ACPI_CPUFREQ CONFIG_X86_ACPI_CPUFREQ
module pata_jmicron did not have configs CONFIG_PATA_JMICRON
module i2c_i801 did not have configs CONFIG_I2C_I801
module serio_raw did not have configs CONFIG_SERIO_RAW
module iTCO_wdt did not have configs CONFIG_ITCO_WDT
module freq_table did not have configs CONFIG_CPU_FREQ_TABLE
module igb did not have configs CONFIG_IGB
module ipv6 did not have configs CONFIG_IPV6
module dca did not have configs CONFIG_DCA
module sunrpc did not have configs CONFIG_SUNRPC
module pata_acpi did not have configs CONFIG_PATA_ACPI
module dm_multipath did not have configs CONFIG_DM_MULTIPATH
module cpufreq_ondemand did not have configs 
CONFIG_CPU_FREQ_GOV_ONDEMAND
module i2c_core did not have configs CONFIG_I2C
module pcspkr did not have configs CONFIG_INPUT_PCSPKR

Of those drivers, igb is the only truly boot-critical one - the box 
wont be very useful if it has no network support.

Another comment: 'make localyesconfig' does not seem to be 
self-invariant. I.e. it does not handle the case well when we 
already have booted a localyesconfig kernel and do 'make 
localyesconfig' again. It will find no modules and will merrily 
create an almost empty .config.

This could be addressed the following way: i think the script should 
implicitly turn on CONFIG_IKCONFIG=y, and should also check for the 
presence of /proc/config.gz and use it as a starting point. This 
makes the whole concept nicely self-invariant.

	Ingo
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