Why ELF format is considered harmful for the speed of Linker?

[cireu]

I see the https://github.com/rui314/mold/blob/main/docs/design.md and @rui314 left a note here

Sometimes, the ELF file format itself seems to be a limiting factor in improving the linker's performance.

I'm not so familar with the linker technology, but I'm quite curios of what makes ELF bad for linker's perfomance.

Answers will be appreciated.

[rui314]

Since I proved otherwise, it is not a valid concern.