linux-kernel - Re: [PATCH bpf-next 0/2] Allow mmap of /sys/kernel/btf/vmlinux

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Message-Id: <ec03896b-feac-4fa5-a213-7e9f57e15f72@app.fastmail.com>
Date: Thu, 01 May 2025 08:58:46 -0700
From: "Daniel Xu" <dxu@...uu.xyz>
To: "Lorenz Bauer" <lmb@...valent.com>, "Arnd Bergmann" <arnd@...db.de>,
 "Alexei Starovoitov" <ast@...nel.org>,
 "Daniel Borkmann" <daniel@...earbox.net>,
 "Andrii Nakryiko" <andrii@...nel.org>,
 "Martin KaFai Lau" <martin.lau@...ux.dev>,
 "Eduard Zingerman" <eddyz87@...il.com>, "Song Liu" <song@...nel.org>,
 "Yonghong Song" <yonghong.song@...ux.dev>,
 "John Fastabend" <john.fastabend@...il.com>, "KP Singh" <kpsingh@...nel.org>,
 "Stanislav Fomichev" <sdf@...ichev.me>, "Hao Luo" <haoluo@...gle.com>,
 "Jiri Olsa" <jolsa@...nel.org>, "Mykola Lysenko" <mykolal@...com>,
 "Shuah Khan" <shuah@...nel.org>
Cc: linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
 "bpf@...r.kernel.org" <bpf@...r.kernel.org>, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH bpf-next 0/2] Allow mmap of /sys/kernel/btf/vmlinux

On Thu, May 1, 2025, at 7:28 AM, Lorenz Bauer wrote:
> I'd like to cut down the memory usage of parsing vmlinux BTF in ebpf-go.
> With some upcoming changes the library is sitting at 5MiB for a parse.
> Most of that memory is simply copying the BTF blob into user space.
> By allowing vmlinux BTF to be mmapped read-only into user space I can
> cut memory usage by about 75%.

Cool! Maybe teach libbpf to use this as well? So everyone else can pick up
the win transparently.

>
> Signed-off-by: Lorenz Bauer <lmb@...valent.com>
> ---
> Lorenz Bauer (2):
>       btf: allow mmap of vmlinux btf
>       selftests: bpf: add a test for mmapable vmlinux BTF
>
>  include/asm-generic/vmlinux.lds.h                  |  3 +-
>  kernel/bpf/sysfs_btf.c                             | 25 ++++++-
>  tools/testing/selftests/bpf/prog_tests/btf_sysfs.c | 79 ++++++++++++++++++++++
>  3 files changed, 104 insertions(+), 3 deletions(-)
> ---
> base-commit: 38d976c32d85ef12dcd2b8a231196f7049548477
> change-id: 20250501-vmlinux-mmap-2ec5563c3ef1
>
> Best regards,
> -- 
> Lorenz Bauer <lmb@...valent.com>