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

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Message-ID: <CAErzpmt85U7ggSpE+2u88C+kh+1JSnvZtW+Qx7c3xDLoHCbNtQ@mail.gmail.com>
Date: Fri, 19 Dec 2025 13:41:08 +0800
From: Donglin Peng <dolinux.peng@...il.com>
To: Andrii Nakryiko <andrii.nakryiko@...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 Fri, Dec 19, 2025 at 8:02 AM Andrii Nakryiko
<andrii.nakryiko@...il.com> wrote:
>
> 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);

Thanks, I will do it.

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