netdev - Re: [PATCHv2 0/3] perf tools: Fix prologue generation

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Message-ID: <CAEf4BzbK9zgetgE1yKkCANTZqizUrXgamJa2X0f0XmzQUdFrCQ@mail.gmail.com>
Date:   Tue, 10 May 2022 16:48:55 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Jiri Olsa <jolsa@...nel.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        "linux-perf-use." <linux-perf-users@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        Ian Rogers <irogers@...gle.com>
Subject: Re: [PATCHv2 0/3] perf tools: Fix prologue generation

On Tue, May 10, 2022 at 12:47 AM Jiri Olsa <jolsa@...nel.org> wrote:
>
> hi,
> sending change we discussed some time ago [1] to get rid of
> some deprecated functions we use in perf prologue code.
>
> Despite the gloomy discussion I think the final code does
> not look that bad ;-)
>
> This patchset removes following libbpf functions from perf:
>   bpf_program__set_prep
>   bpf_program__nth_fd
>   struct bpf_prog_prep_result
>
> v2 changes:
>   - use fallback section prog handler, so we don't need to
>     use section prefix [Andrii]
>   - realloc prog->insns array in bpf_program__set_insns [Andrii]
>   - squash patch 1 from previous version with
>     bpf_program__set_insns change [Daniel]
>   - patch 3 already merged [Arnaldo]
>   - added more comments
>
>   meanwhile.. perf/core and bpf-next diverged, so:
>     - libbpf bpf_program__set_insns change is based on bpf-next/master
>     - perf changes do not apply on bpf-next/master so they are based on
>       perf/core ... however they can be merged only after we release
>       libbpf 0.8.0 with bpf_program__set_insns change, so we don't break
>       the dynamic linking
>       I'm sending perf changes now just for review, I'll resend them
>       once libbpf 0.8.0 is released
>
> thanks,
> jirka
>
>
> [1] https://lore.kernel.org/bpf/CAEf4BzaiBO3_617kkXZdYJ8hS8YF--ZLgapNbgeeEJ-pY0H88g@mail.gmail.com/
> ---
> Jiri Olsa (1):
>       libbpf: Add bpf_program__set_insns function
>

The first patch looks good to me. The rest I can't really review and
test properly, so I'll leave it up to Arnaldo.

Arnaldo, how do we coordinate these patches? Should they go through
bpf-next (after you Ack them) or you want them in your tree?

I'd like to get the bpf_program__set_insns() patch into bpf-next so
that I can do libbpf v0.8 release, having it in a separate tree is
extremely inconvenient. Please let me know how you think we should
proceed?

>  tools/lib/bpf/libbpf.c   | 22 ++++++++++++++++++++++
>  tools/lib/bpf/libbpf.h   | 18 ++++++++++++++++++
>  tools/lib/bpf/libbpf.map |  1 +
>  3 files changed, 41 insertions(+)
>
> Jiri Olsa (2):
>       perf tools: Register fallback libbpf section handler
>       perf tools: Rework prologue generation code
>
>  tools/perf/util/bpf-loader.c | 175 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-------------
>  1 file changed, 157 insertions(+), 18 deletions(-)