[v1] Allow mmap of /sys/kernel/btf/vmlinux

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

Lorenz Bauer posted 2 patches 9 months, 1 week ago

Diff against v2 v3 v4 v5
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There is a newer version of this series

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(-)

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

Posted by Lorenz Bauer 9 months, 1 week ago

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%.

Signed-off-by: Lorenz Bauer <lmb@isovalent.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@isovalent.com>

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

Posted by Daniel Xu 9 months, 1 week ago

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@isovalent.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@isovalent.com>