Re: How to deal with increased install size with `CONFIG_DEBUG_INFO_BTF=y`

[Yonghong Song <yonghong.song@linux.dev>]

On 8/25/25 8:42 AM, Paul Menzel wrote:
> Dear Linux folks,
>
>
> Trying to get ptcpdump [1] running, I needed to build Linux with BTF 
> symbols.
>
> ```
> @@ -5985,11 +5986,22 @@
>  #
>  # Compile-time checks and compiler options
>  #
> +CONFIG_DEBUG_INFO=y
>  CONFIG_AS_HAS_NON_CONST_ULEB128=y
> -CONFIG_DEBUG_INFO_NONE=y
> +# CONFIG_DEBUG_INFO_NONE is not set
>  # CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT is not set
>  # CONFIG_DEBUG_INFO_DWARF4 is not set
> -# CONFIG_DEBUG_INFO_DWARF5 is not set
> +CONFIG_DEBUG_INFO_DWARF5=y
> +# CONFIG_DEBUG_INFO_REDUCED is not set
> +CONFIG_DEBUG_INFO_COMPRESSED_NONE=y
> +# CONFIG_DEBUG_INFO_COMPRESSED_ZLIB is not set
> +# CONFIG_DEBUG_INFO_SPLIT is not set
> +CONFIG_DEBUG_INFO_BTF=y
> +CONFIG_PAHOLE_HAS_SPLIT_BTF=y
> +CONFIG_PAHOLE_HAS_LANG_EXCLUDE=y
> +CONFIG_DEBUG_INFO_BTF_MODULES=y
> +# CONFIG_MODULE_ALLOW_BTF_MISMATCH is not set
> +# CONFIG_GDB_SCRIPTS is not set
>  CONFIG_FRAME_WARN=2048
>  # CONFIG_STRIP_ASM_SYMS is not set
>  # CONFIG_READABLE_ASM is not set
> ```
>
> This increased the module size quite a bit:
>
>     $ du -sh /lib/modules/6.12.4*
>     128M        /lib/modules/6.12.40.mx64.484
>     1.9G        /lib/modules/6.12.43.mx64.485

The increase is mostly due to dwarf. The BTF related sections should be just ~6M.

>
> Searching the WWW, it was suggested to run `INSTALL_MOD_STRIP=1` [2], 
> bringing it down to 137 MB:
>
>     137M        /lib/modules/6.12.43.mx64.486
>
> I was under the expression, that BTF symbols are small compared to the 
> debug symbol types from the past. (Excuse my ignorance about the 
> terminology and subject.) Is `INSTALL_MOD_STRIP=1` the “recommended” 
> way to still use BPF/BTF on production systems.

You can use INSTALL_MOD_STRIP=1 to reduce kernel binary size in /lib/modules/... directory.

>
>
> Kind regards,
>
> Paul
>
>
> [1]: https://github.com/mozillazg/ptcpdump
> [2]: 
> https://gitlab.alpinelinux.org/alpine/aports/-/merge_requests/28218/diffs
>