Re: ppc64le vmlinuz is huge when building with BTF

[Eduard Zingerman <eddyz87@gmail.com>]

On Thu, 2023-06-15 at 12:32 +0900, Dominique Martinet wrote:
> Hi,
> 
> coming from alpine: https://gitlab.alpinelinux.org/alpine/aports/-/issues/12563
> 
> alice noticed the kernel packages got quite bigger, in particular for
> ppc64le I've confirmed that the vmlinuz file size jump when building
> with BTF:
> currently released package with BTF:
> https://dl-cdn.alpinelinux.org/alpine/edge/main/ppc64le/linux-lts-6.1.33-r0.apk
> 272M	boot/vmlinuz-lts

Hi Dominique,

I've just checked the linked apk and it looks like DWARF sections are
not stripped and take most of the space, e.g.:

$ llvm-objdump --headers boot/vmlinuz-lts | grep \.debug \
  | gawk '{ sum += strtonum("0x"$3); } END { print sum; }' | numfmt --to iec
228M

Compare this to BTF sections size:

$ llvm-objdump --headers boot/vmlinuz-lts | grep BTF \
  | gawk '{ sum += strtonum("0x"$3); } END { print sum; }' | numfmt --to iec
3,9M

> 
> test build without BTF:
> https://gitlab.alpinelinux.org/martinetd/aports/-/jobs/1049335
> 44M	boot/vmlinuz-lts
> 
> 
> Is that a known issue?
> We'll probably just turn off BTF for the ppc64le build for now, but it
> might be worth checking.
> 
> 
> While I have your attention, even the x86_64 package grew much bigger
> than I thought it would, the installed modules directory go from 90MB to
> 108MB gzipped); it's a 18% increase (including kernel: 103->122MB) which
> is more than what I'd expect out of BTF.
> Most users don't care about BTF so it'd be great if they could be built
> and installed separately (debug package all over again..) or limiting
> the growth a bit more if possible.
> I haven't tried yet but at this point ikheaders is probably worth
> considering instead..
> Perhaps we're missing some stripping option or something?
> 
> 
> Thanks!