linux-kernel - Re: [PATCH bpf-next v10 09/13] bpf: Optimize the performance of find_bpffs_btf

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Message-ID: <CAEf4BzZVFMbP+XXTOedDESKL4jred6vg2L8Dv5C-mmKMp9sicQ@mail.gmail.com>
Date: Thu, 18 Dec 2025 16:01:50 -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 09/13] bpf: Optimize the performance of find_bpffs_btf_enums

On Thu, Dec 18, 2025 at 3:31 AM Donglin Peng <dolinux.peng@...il.com> wrote:
>
> From: pengdonglin <pengdonglin@...omi.com>
>
> Currently, vmlinux BTF is unconditionally sorted during
> the build phase. The function btf_find_by_name_kind
> executes the binary search branch, so find_bpffs_btf_enums
> can be optimized by using btf_find_by_name_kind.
>
> 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>
> Acked-by: Eduard Zingerman <eddyz87@...il.com>
> ---
>  kernel/bpf/inode.c | 42 +++++++++++++++++++-----------------------
>  1 file changed, 19 insertions(+), 23 deletions(-)
>
> diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c
> index 9f866a010dad..050fde1cf211 100644
> --- a/kernel/bpf/inode.c
> +++ b/kernel/bpf/inode.c
> @@ -600,10 +600,18 @@ struct bpffs_btf_enums {
>
>  static int find_bpffs_btf_enums(struct bpffs_btf_enums *info)
>  {
> +       struct {
> +               const struct btf_type **type;
> +               const char *name;
> +       } btf_enums[] = {
> +               {&info->cmd_t,          "bpf_cmd"},
> +               {&info->map_t,          "bpf_map_type"},
> +               {&info->prog_t,         "bpf_prog_type"},
> +               {&info->attach_t,       "bpf_attach_type"},
> +       };
>         const struct btf *btf;
>         const struct btf_type *t;
> -       const char *name;
> -       int i, n;
> +       int i, id;
>
>         memset(info, 0, sizeof(*info));
>
> @@ -615,30 +623,18 @@ static int find_bpffs_btf_enums(struct bpffs_btf_enums *info)
>
>         info->btf = btf;
>
> -       for (i = 1, n = btf_nr_types(btf); i < n; i++) {
> -               t = btf_type_by_id(btf, i);
> -               if (!btf_type_is_enum(t))
> -                       continue;
> +       for (i = 0; i < ARRAY_SIZE(btf_enums); i++) {
> +               id = btf_find_by_name_kind(btf, btf_enums[i].name,
> +                                          BTF_KIND_ENUM);
> +               if (id < 0)
> +                       goto out;
>
> -               name = btf_name_by_offset(btf, t->name_off);
> -               if (!name)
> -                       continue;

return -ESRCH, why goto at all?

> -
> -               if (strcmp(name, "bpf_cmd") == 0)
> -                       info->cmd_t = t;
> -               else if (strcmp(name, "bpf_map_type") == 0)
> -                       info->map_t = t;
> -               else if (strcmp(name, "bpf_prog_type") == 0)
> -                       info->prog_t = t;
> -               else if (strcmp(name, "bpf_attach_type") == 0)
> -                       info->attach_t = t;
> -               else
> -                       continue;
> -
> -               if (info->cmd_t && info->map_t && info->prog_t && info->attach_t)
> -                       return 0;
> +               t = btf_type_by_id(btf, id);
> +               *btf_enums[i].type = t;

nit: drop t local variable, just assign directly:

*btf_enums[i].type = btf_type_by_id(btf, id);

>         }
>
> +       return 0;
> +out:
>         return -ESRCH;
>  }
>
> --
> 2.34.1
>