Re: [PATCH 2.5] Retrieve configuration information from kernel

[Khalid Aziz]

Padraig Brady wrote:
> 
> Khalid Aziz wrote:
> > Paul Clements wrote:
> >
> >>Have you considered compressing the config info in order to reduce
> >>the space wastage in the loaded kernel image? Could easily be 10's of KB
> >>(not that that's a lot these days). The info would then be retrieved via
> >>"gunzip -c", et al. instead of a simple "cat".
> >
> > I wanted to start with a simple implementation first. There are a couple
> > of things that can be done in future to further improve meory usage: (1)
> > Drop "CONFIG_" and "# CONFIG_" from each line and add it back when
> > printing from /proc/ikconfig and extract-ikconfig script, (2) Compress
> > the resulting configuration. Something to do in near future :)
> 
> $ wc -c /usr/src/linux-2.4/.config
>    38092 /usr/src/linux-2.4/.config

That charcater count includes all the comments as well. It may not be
much but it is not insignificant.

# wc -c .config
  22174 .config
# grep "^#\? \?CONFIG_"  .config | wc -c
  20623

> $ gzip -c /usr/src/linux-2.4/.config | wc -c
>    10305
> $ sed '/^ *$/d;/^#/d;s/^CONFIG_//'  /usr/src/linux-2.4/.config | wc -c
>    17267
> $ sed '/^ *$/d;/^#/d;s/^CONFIG_//'  /usr/src/linux-2.4/.config | gzip | wc -c
>     6155

Dropping "CONFIG_" and "# CONFIG_" will definitely reduce memory
requirements. We do not want to drop the lines "# CONFIG_* is not set".
If you do that, you end up having to answer lots of questions when
running "make oldconfig".
 
> 
> Also it seems like it would be more useful to have the config in the
> kernel image rather than (just) proc?

It IS in the kernel image. Use scripts/extract-ikconfig to extract it
from the kernel image file. And if you only need it to be in kernel
image, you can choose to not have it under /proc.

--
Khalid 

====================================================================
Khalid Aziz                                Linux and Open Source Lab
[phone]                                        Hewlett-Packard
[e-mail]                                       Fort Collins, CO

"The Linux kernel is subject to relentless development" 
				- Alessandro Rubini