linux-kernel - Re: [PATCH bpf-next v10 10/13] libbpf: Optimize the performance of determine_ptr

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Message-ID: <CAEf4BzZG9i9uVSyPq=6=t7KDgxvXX6GgDkKA4fCd11Un5HQJhQ@mail.gmail.com>
Date: Thu, 18 Dec 2025 16:03:35 -0800
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Donglin Peng <dolinux.peng@...il.com>
Cc: ast@...nel.org, eddyz87@...il.com, zhangxiaoqin@...omi.com, 
	ihor.solodrai@...ux.dev, linux-kernel@...r.kernel.org, bpf@...r.kernel.org, 
	pengdonglin <pengdonglin@...omi.com>, Alan Maguire <alan.maguire@...cle.com>
Subject: Re: [PATCH bpf-next v10 10/13] libbpf: Optimize the performance of determine_ptr_size

On Thu, Dec 18, 2025 at 3:31 AM Donglin Peng <dolinux.peng@...il.com> wrote:
>
> From: pengdonglin <pengdonglin@...omi.com>
>
> Leverage the performance improvement of btf__find_by_name_kind() when
> BTF is sorted. For sorted BTF, the function uses binary search with
> O(log n) complexity instead of linear search, providing significant
> performance benefits, especially for large BTF like vmlinux.
>
> Cc: Eduard Zingerman <eddyz87@...il.com>
> Cc: Alexei Starovoitov <ast@...nel.org>
> Cc: Andrii Nakryiko <andrii.nakryiko@...il.com>
> Cc: Alan Maguire <alan.maguire@...cle.com>
> Cc: Ihor Solodrai <ihor.solodrai@...ux.dev>
> Cc: Xiaoqin Zhang <zhangxiaoqin@...omi.com>
> Signed-off-by: pengdonglin <pengdonglin@...omi.com>
> ---
>  tools/lib/bpf/btf.c | 20 ++++++--------------
>  1 file changed, 6 insertions(+), 14 deletions(-)
>

nice and clean

Acked-by: Andrii Nakryiko <andrii@...nel.org>

> diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
> index c63d46b7d74b..b5b0898d033d 100644
> --- a/tools/lib/bpf/btf.c
> +++ b/tools/lib/bpf/btf.c
> @@ -659,29 +659,21 @@ static int determine_ptr_size(const struct btf *btf)
>                 "int long unsigned",
>         };
>         const struct btf_type *t;
> -       const char *name;
> -       int i, j, n;
> +       int i, id;
>
>         if (btf->base_btf && btf->base_btf->ptr_sz > 0)
>                 return btf->base_btf->ptr_sz;
>
> -       n = btf__type_cnt(btf);
> -       for (i = 1; i < n; i++) {
> -               t = btf__type_by_id(btf, i);
> -               if (!btf_is_int(t))
> +       for (i = 0; i < ARRAY_SIZE(long_aliases); i++) {
> +               id = btf__find_by_name_kind(btf, long_aliases[i], BTF_KIND_INT);
> +               if (id < 0)
>                         continue;
>
> +               t = btf__type_by_id(btf, id);
>                 if (t->size != 4 && t->size != 8)
>                         continue;
>
> -               name = btf__name_by_offset(btf, t->name_off);
> -               if (!name)
> -                       continue;
> -
> -               for (j = 0; j < ARRAY_SIZE(long_aliases); j++) {
> -                       if (strcmp(name, long_aliases[j]) == 0)
> -                               return t->size;
> -               }
> +               return t->size;
>         }
>
>         return -1;
> --
> 2.34.1
>