Re: [PATCHv4 bpf-next 0/5] bpf: Speed up symbol resolving in kprobe multi link

Andrii Nakryiko
2022-04-29T14:28:31Z

On Thu, Apr 28, 2022 at 1:12 PM Jiri Olsa <jolsa@kernel.org> wrote:
>
> hi,
> sending additional fix for symbol resolving in kprobe multi link
> requested by Alexei and Andrii [1].
>
> This speeds up bpftrace kprobe attachment, when using pure symbols
> (3344 symbols) to attach:
>
> Before:
>
> # perf stat -r 5 -e cycles ./src/bpftrace -e 'kprobe:x* { } i:ms:1 { exit(); }'
> ...
> 6.5681 +- 0.0225 seconds time elapsed ( +- 0.34% )
>
> After:
>
> # perf stat -r 5 -e cycles ./src/bpftrace -e 'kprobe:x* { } i:ms:1 { exit(); }'
> ...
> 0.5661 +- 0.0275 seconds time elapsed ( +- 4.85% )
>
> v4 changes:
> - fix compile issue [kernel test robot]
> - added acks [Andrii]
>
> v3 changes:
> - renamed kallsyms_lookup_names to ftrace_lookup_symbols
> and moved it to ftrace.c [Masami]
> - added ack [Andrii]
> - couple small test fixes [Andrii]
>
> v2 changes (first version [2]):
> - removed the 2 seconds check [Alexei]
> - moving/forcing symbols sorting out of kallsyms_lookup_names function [Alexei]
> - skipping one array allocation and copy_from_user [Andrii]
> - several small fixes [Masami,Andrii]
> - build fix [kernel test robot]
>
> thanks,
> jirka
>
>
> [1] https://lore.kernel.org/bpf/CAEf4BzZtQaiUxQ-sm_hH2qKPRaqGHyOfEsW96DxtBHRaKLoL3Q@mail.gmail.com/
> [2] https://lore.kernel.org/bpf/20220407125224.310255-1-jolsa@kernel.org/
> ---
> Jiri Olsa (5):
> kallsyms: Fully export kallsyms_on_each_symbol function
> ftrace: Add ftrace_lookup_symbols function
> fprobe: Resolve symbols with ftrace_lookup_symbols
> bpf: Resolve symbols with ftrace_lookup_symbols for kprobe multi link
> selftests/bpf: Add attach bench test
>

Please check [0], it reports rcu_read_unlock() misuse

[0] https://github.com/kernel-patches/bpf/runs/6223167405?check_suite_focus=true

> include/linux/ftrace.h | 6 ++++++
> include/linux/kallsyms.h | 7 ++++++-
> kernel/kallsyms.c | 3 +--
> kernel/trace/bpf_trace.c | 112 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++----------------------------------------------
> kernel/trace/fprobe.c | 32 ++++++++++++--------------------
> kernel/trace/ftrace.c | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c | 133 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> tools/testing/selftests/bpf/progs/kprobe_multi_empty.c | 12 ++++++++++++
> 8 files changed, 298 insertions(+), 69 deletions(-)
> create mode 100644 tools/testing/selftests/bpf/progs/kprobe_multi_empty.c