linux-kernel - Re: [RFC PATCH v2 5/5] btf: add CONFIG_BPF_SORT_BTF_BY_KIND

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Message-ID: <CAErzpmuSEfgih1-RDN1FAxB5Sd1phKr9Ntr9YmdDw2vXGgZ0Gw@mail.gmail.com>
Date: Wed, 22 Oct 2025 09:15:21 +0800
From: Donglin Peng <dolinux.peng@...il.com>
To: Alan Maguire <alan.maguire@...cle.com>
Cc: ast@...nel.org, linux-kernel@...r.kernel.org, bpf@...r.kernel.org, 
	Eduard Zingerman <eddyz87@...il.com>, Andrii Nakryiko <andrii.nakryiko@...il.com>, 
	Song Liu <song@...nel.org>, pengdonglin <pengdonglin@...omi.com>
Subject: Re: [RFC PATCH v2 5/5] btf: add CONFIG_BPF_SORT_BTF_BY_KIND_NAME

On Wed, Oct 22, 2025 at 1:28 AM Alan Maguire <alan.maguire@...cle.com> wrote:
>
> On 20/10/2025 10:39, Donglin Peng wrote:
> > Pahole v1.32 and later supports BTF sorting. Add a new configuration
> > option to control whether to enable this feature for vmlinux and
> > kernel modules.
> >
> > 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: Song Liu <song@...nel.org>
> > Signed-off-by: pengdonglin <pengdonglin@...omi.com>
> > Signed-off-by: Donglin Peng <dolinux.peng@...il.com>
> > ---
> >  kernel/bpf/Kconfig   | 8 ++++++++
> >  scripts/Makefile.btf | 5 +++++
> >  2 files changed, 13 insertions(+)
> >
> > diff --git a/kernel/bpf/Kconfig b/kernel/bpf/Kconfig
> > index eb3de35734f0..08251a250f06 100644
> > --- a/kernel/bpf/Kconfig
> > +++ b/kernel/bpf/Kconfig
> > @@ -101,4 +101,12 @@ config BPF_LSM
> >
> >         If you are unsure how to answer this question, answer N.
> >
> > +config BPF_SORT_BTF_BY_KIND_NAME
> > +     bool "Sort BTF types by kind and name"
> > +     depends on BPF_SYSCALL
> > +     help
> > +       This option sorts BTF types in vmlinux and kernel modules by their
> > +       kind and name, enabling binary search for btf_find_by_name_kind()
> > +       and significantly improving its lookup performance.
> > +
> >  endmenu # "BPF subsystem"
> > diff --git a/scripts/Makefile.btf b/scripts/Makefile.btf
> > index db76335dd917..3f1a0b3c3f3f 100644
> > --- a/scripts/Makefile.btf
> > +++ b/scripts/Makefile.btf
> > @@ -29,6 +29,11 @@ ifneq ($(KBUILD_EXTMOD),)
> >  module-pahole-flags-$(call test-ge, $(pahole-ver), 128) += --btf_features=distilled_base
> >  endif
> >
> > +ifeq ($(call test-ge, $(pahole-ver), 132),y)
> > +pahole-flags-$(CONFIG_BPF_SORT_BTF_BY_KIND_NAME)     += --btf_features=sort
> > +module-pahole-flags-$(CONFIG_BPF_SORT_BTF_BY_KIND_NAME) += --btf_features=sort
> > +endif
> > +
>
> perhaps it's useful informationally, but you don't need to wrap the
> addition of the sort flag in a pahole version check; unsupported
> btf_features are just ignored. Also we're at v1.30 in pahole now (we'll
> be releasing 1.31 shortly hopefully), so any version check should be
> v1.30/v1.31. I'd say just leave out the version check though.

Understood, thanks. Will do.

>
> Alan