Take the tour ×  I'm running Ubuntu 11.10, which came with
kernel version 3.0.0-14. I downloaded and built a kernel from
the 3.1.0 branch. After installing the new kernel, I see that my
/boot/initrd.img-3.1.0 file is HUGE. It's 114MB, while my
/boot/initrd.img-3.0.0-14-generic is about 13MB. I want to get
rid of the bloat, which is clearly unnecessary.  When building
the new kernel, I copied my /boot/config-3.0.0-14-generic to
.config in my build directory, as to keep the configuration of
my original kernel. I ran make oldconfig, selected the defaults
for all the new options, and then built the kernel.  Looking at
the file sizes within each of the initrd cpio archives, I see
that all of my .ko modules are larger in size in the 3.1.0
ramdisk, than the 3.0.0-14. I assumed there was an unnecessary
debug flag checked in my config file, but I don't see anything
different that was not already enabled in the 3.0.0-14 config
file.  My /boot/config-3.0.0-14-generic is here:
http://pastebin.com/UjH7nEqd  And my /boot/c