[RFC PATCH bpf-next 0/2] bpf: Add generic kfunc bpf_ffs64()

[Leon Hwang <hffilwlqm@gmail.com>]

This patchset introduces a new generic kfunc bpf_ffs64(). This kfunc
allows bpf to reuse kernel's __ffs64() function to improve ffs
performance in bpf.

In patch "bpf: Add generic kfunc bpf_ffs64()", there is some data to
confirm that this kfunc is able to save around 10ns for every time on
"Intel(R) Xeon(R) Silver 4116 CPU @ 2.10GHz" CPU server, by comparing
with bpf-implemented __ffs64().

However, it will be better when convert this kfunc to "rep bsf" in
JIT on x86, which is able to avoid a call. But, I haven't figure out the
way.

Leon Hwang (2):
  bpf: Add generic kfunc bpf_ffs64()
  selftests/bpf: Add testcases for generic kfunc bpf_ffs64()

 kernel/bpf/helpers.c                          |  7 +++
 .../testing/selftests/bpf/prog_tests/bitops.c | 54 +++++++++++++++++++
 tools/testing/selftests/bpf/progs/bitops.c    | 21 ++++++++
 3 files changed, 82 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/bitops.c
 create mode 100644 tools/testing/selftests/bpf/progs/bitops.c


base-commit: c5809f0c308111adbcdbf95462a72fa79eb267d1
-- 
2.42.1