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

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Date:   Fri, 20 May 2022 14:46:49 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Jiri Olsa <olsajiri@...il.com>
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 Thu, May 19, 2022 at 4:03 AM Jiri Olsa <olsajiri@...il.com> wrote:
>
> On Wed, May 18, 2022 at 11:46:44AM +0200, Jiri Olsa wrote:
> > On Tue, May 17, 2022 at 03:02:53PM -0700, Andrii Nakryiko wrote:
> > > On Wed, May 11, 2022 at 11:22 AM Arnaldo Carvalho de Melo
> > > <acme@...nel.org> wrote:
> > > >
> > > > Em Wed, May 11, 2022 at 09:35:34AM +0200, Jiri Olsa escreveu:
> > > > > On Tue, May 10, 2022 at 04:48:55PM -0700, Andrii Nakryiko wrote:
> > > > > > 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?
> > > > >
> > > > > we need to wait with perf changes after the libbpf is merged and
> > > > > libbpf 0.8.0 is released.. so we don't break dynamic linking for
> > > > > perf
> > > > >
> > > > > at the moment please just take libbpf change and I'll resend the
> > > > > perf change later if needed
> > > >
> > > > Ok.
> > > >
> > >
> > > Jiri, libbpf v0.8 is out, can you please re-send your perf patches?
> >
> > yep, just made new fedora package.. will resend the perf changes soon
>
> fedora package is on the way, but I'll need perf/core to merge
> the bpf_program__set_insns change.. Arnaldo, any idea when this
> could happen?
>

Jiri, Arnaldo,

Can we land these patches through bpf-next to avoid such complicated
cross-tree dependencies? As I started removing libbpf APIs I also
noticed that perf is still using few other deprecated APIs:
  - bpf_map__next;
  - bpf_program__next;
  - bpf_load_program;
  - btf__get_from_id;

It's trivial to fix up, but doing it across few trees will delay
libbpf work as well.

So let's land this through bpf-next, if Arnaldo doesn't mind?

> thanks,
> jirka