[yocto] more efficient debug kernel

[Bruce Ashfield]

On 10/18/2017 06:29 PM, Robert Berger wrote:
> Hi,
> 
> I usually build a debug kernel with debug info included, which makes it 
> run "suboptimal". Distros build the kernel with CONFIG_DEBUG_INFO 
> enables, but strip symbols out of the resulting kernel and kernel 
> modules, and place them in the separate debuginfo packages. This makes 
> the kernel much smaller and also makes it run more efficiently because 
> of caching.
> 
> Is this possible with the Yocto kernel tooling as well?

That isn't something that I've ever done via oe-core or the
Yocto kernel tooling.

We can absolutely support different kernel types, and in fact,
do have a developer/debug kernel and a production kernel variant.
But they are typically built and packaged separately rather than
being generated from the same build.

There is also a strip() routine for the kernel, but it only
operates on vmlinux (and was used to keep very large images
under bootloader size restrictions). I'd see this as something
that could definitely be done in a 2nd phase part of a build,
since it is just processing already created binaries (maybe
someone does have such a thing in a custom layer).

The multiple image builds, kernel module splitting, upgrade
paths, multilibs, etc, all make the packaging pretty complex
already, but there might be something in this area that could
be done.

I had an old bugzilla entry about kernel-dev packaging: 
https://bugzilla.yoctoproject.org/show_bug.cgi?id=7095,
but it didn't touch on this issue.

That being said, maybe there already is something that the core
packaging classes are doing (I just looked at my latest kernel
build and didn't see anything) .. and that I'm just missing ..
if so, hopefully someone else will enlighten us :D

Bruce

> 
> Regards,
> 
> Robert