On Mon, Feb 4, 2019 at 5:32 PM Daniel Borkmann [off-list ref] wrote:

Hi Andrii,

On 01/31/2019 07:58 AM, Andrii Nakryiko wrote:

quoted

This patch series adds BTF deduplication algorithm to libbpf. This algorithm
allows to take BTF type information containing duplicate per-compilation unit
information and reduce it to equivalent set of BTF types with no duplication without
loss of information. It also deduplicates strings and removes those strings that
are not referenced from any BTF type (and line information in .BTF.ext section,
if any).

Algorithm also resolves struct/union forward declarations into concrete BTF types
across multiple compilation units to facilitate better deduplication ratio. If
undesired, this resolution can be disabled through specifying corresponding options.

When applied to BTF data emitted by pahole's DWARF->BTF converter, it reduces
the overall size of .BTF section by about 65x, from about 112MB to 1.75MB, leaving
only 29247 out of initial 3073497 BTF type descriptors.

Algorithm with minor differences and preliminary results before FUNC/FUNC_PROTO
support is also described more verbosely at:
https://facebookmicrosites.github.io/bpf/blog/2018/11/14/btf-enhancement.html

Andrii Nakryiko (3):
  btf: extract BTF type size calculation
  btf: add BTF types deduplication algorithm
  selftests/btf: add initial BTF dedup tests

 tools/lib/bpf/btf.c                    | 1851 +++++++++++++++++++++++-
 tools/lib/bpf/btf.h                    |   11 +
 tools/lib/bpf/libbpf.map               |    3 +
 tools/testing/selftests/bpf/test_btf.c |  535 ++++++-
 4 files changed, 2333 insertions(+), 67 deletions(-)

This would need a proper rebase for bpf-next so that it applies w/o
bigger conflicts. Please also change the libbpf.map and place the newly
exported functions under LIBBPF_0.0.2 (as everything under 0.0.1 was from
prior released kernel).

Done. Thanks!

Thanks,
Daniel