Re: [PATCH bpf-next v2 14/18] libbpf: add btf type hash lookup support

[Andrii Nakryiko <andrii.nakryiko@gmail.com>]

On Thu, Jul 3, 2025 at 5:22 AM Menglong Dong <menglong8.dong@gmail.com> wrote:
>
> For now, the libbpf find the btf type id by loop all the btf types and
> compare its name, which is inefficient if we have many functions to
> lookup.
>
> We add the "use_hash" to the function args of find_kernel_btf_id() to
> indicate if we should lookup the btf type id by hash. The hash table will
> be initialized if it has not yet.

Or we could build hashtable-based index outside of struct btf for a
specific use case, because there is no one perfect hashtable-based
indexing that can be done generically (e.g., just by name, or
name+kind, or kind+name, or some more complicated lookup key) and
cover all potential use cases. I'd prefer not to get into a problem of
defining and building indexes and leave it to callers (even if the
caller is other part of libbpf itself).

>
> Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
> ---
>  tools/lib/bpf/btf.c      | 102 +++++++++++++++++++++++++++++++++++++++
>  tools/lib/bpf/btf.h      |   6 +++
>  tools/lib/bpf/libbpf.c   |  37 +++++++++++---
>  tools/lib/bpf/libbpf.map |   3 ++
>  4 files changed, 140 insertions(+), 8 deletions(-)
>

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