Huge difference in build sizes

[greg@kroah.com (Greg KH)]

On Wed, Dec 03, 2014 at 09:26:34AM +0530, Raghavendra wrote:
> Hello Greg,
> 
> Thank you for the reply.
> 
> On Tuesday 02 December 2014 11:46 PM, Greg KH wrote:
> >On Tue, Dec 02, 2014 at 02:38:27PM +0530, Raghavendra wrote:
> >>Hello all,
> >>
> >>I am using Ubuntu-12.04 which came with 3.2 kernel. Parallel to this,
> >>I've compiled and installed 3.12.1 kernel using the Ubuntu-3.2's
> >>configuration, and the compiler which came with the distro. I've noticed
> >>that there is a huge difference in the size of the .ko file between the
> >>Ubuntu's kernel and the kernel which I've compiled. Sample results are :
> >>
> >>$ du -sh usb-storage.ko
> >>It shows : 56K for the Ubuntu's 3.2 kernel
> >>                  1.3M for the custom kernel that I've compiled
> >>
> >>I've tested the same thing for a simple hello world module :
> >>$ du -sh hello.ko
> >>It shows : 4.0k for the Ubuntu's 3.2 kernel
> >>                  56k for the custom kernel that I've compiled
> >>
> >>What could be the reason for this huge amount of difference of storage
> >>space in spite of using the same config file and compiler?
> >You have not "stripped" the debug symbols from the kernel you built,
> >which is what Ubuntu does as part of their build process.  I suggest
> >turning off that kernel configuration option, as it's probably not
> >needed for your development.
> If you are referring to the option "CONFIG_DEBUG_INFO", then it is said to
> 'y' in both the kernel's configuration files.
> Is there any other config. option or compiler flags that I need to look for?

That's a good one to turn off, start with that and see what happens.