Re: [RFC PATCH v7 5/7] libbpf: Implement BTF type sorting validation for binary search optimization

[Eduard Zingerman <eddyz87@gmail.com>]

On Sat, 2025-11-22 at 00:50 -0800, Eduard Zingerman wrote:

[...]

> > Thanks. I’ve looked into find_btf_percpu_datasec and we can’t use
> > btf_find_by_name_kind here because the search scope differs. For
> > a module BTF, find_btf_percpu_datasec only searches within the
> > module’s own BTF, whereas btf_find_by_name_kind prioritizes
> > searching the base BTF first. Thus, placing named types ahead is
> > more effective here. Besides, I found that the '.data..percpu' named
> > type will be placed at [1] for vmlinux BTF because the prefix '.' is
> > smaller than any letter, so the linear search only requires one loop to
> > locate it. However, if we put named types at the end, it will need more
> > than 60,000 loops..
> 
> But this can be easily fixed if a variant of btf_find_by_name_kind()
> is provided that looks for a match only in a specific BTF. Or accepts
> a start id parameter.

Also, I double checked, and for my vmlinux the id for '.data..percpu'
section is 110864, the last id of all. So, having all anonymous types
in front does not change status-quo compared to current implementation.